The CVS version compiles fine on Solaris but Mesa 6.5 has problems
to build for sunos5-gcc.

Making programs for sunos5-gcc
make[3]: Entering directory `/export/home/egger/src/mesa/Mesa-6.5/progs/demos'
gcc -c -I../../include -Wall -O3 -g -fomit-frame-pointer -pipe -fPIC  -D_REENTRA
                                                                            NT
-DUSE_XSHM -DUSE_SPARC_ASM -std=c99 -ffast-math -I/usr/openwin/include readte  
                                                                          x.c
gcc -I../../include -Wall -O3 -g -fomit-frame-pointer -pipe -fPIC  -D_REENTRANT
                                                                            
-DUSE_XSHM -DUSE_SPARC_ASM -std=c99 -ffast-math -I/usr/openwin/include arbfpligh
                                                                            t.c
readtex.o -L../../lib -lX11 -lglut -lGLU -lGL -lm -o arbfplight
Undefined                       first referenced
 symbol                             in file
glGetQueryObjecti64vEXT             ../../lib/libGL.so
glBlitFramebufferEXT                ../../lib/libGL.so
glGetQueryObjectui64vEXT            ../../lib/libGL.so
ld: fatal: Symbol referencing errors. No output written to arbfplight
collect2: ld returned 1 exit status
make[3]: *** [arbfplight] Error 1
make[3]: Leaving directory `/export/home/egger/src/mesa/Mesa-6.5/progs/demos'
make[2]: *** [subdirs] Error 1
make[2]: Leaving directory `/export/home/egger/src/mesa/Mesa-6.5/progs'
make[1]: *** [default] Error 1
make[1]: Leaving directory `/export/home/egger/src/mesa/Mesa-6.5'

(I use gcc 3.4.2 from sunfreeware)
That bug could be fixed in CVS but I'm not sure if it compiles for 
name mangling:
Ok I try it with -DUSE_MGL_NAMESPACE added to the DEFINES in sunos5-gcc

Making programs for sunos5-gcc
make[3]: Entering directory `/export/home/egger/src/mesa/Mesa-6.5/progs/demos'
gcc -c -I../../include -Wall -O3 -g -fomit-frame-pointer -pipe -fPIC 
-D_REENTRANT -DUSE_XSHM -DUSE_MGL_NAMESPACE -DUSE_SPARC_ASM -std=c99 -ffast-math
-I/usr/openwin/include readtex.c
gcc -I../../include -Wall -O3 -g -fomit-frame-pointer -pipe -fPIC  -D_REENTRANT
-DUSE_XSHM -DUSE_MGL_NAMESPACE -DUSE_SPARC_ASM -std=c99 -ffast-math
-I/usr/openwin/include arbfplight.c readtex.o -L../../lib -lX11 -lglut -lGLU
-lGL -lm -o arbfplight
Undefined                       first referenced
 symbol                             in file
mglGetMinmax                        ../../lib/libGL.so
mglNormal3fv                        ../../lib/libglut.so
mglNormal3dv                        ../../lib/libGL.so
mglNormal3bv                        ../../lib/libGL.so
mglNormal3iv                        ../../lib/libGL.so
mglNormal3sv                        ../../lib/libGL.so
mglSecondaryColor3s                 ../../lib/libGL.so
mglSecondaryColor3b                 ../../lib/libGL.so
mglSecondaryColor3d                 ../../lib/libGL.so
mglSecondaryColor3f                 ../../lib/libGL.so
mglSecondaryColor3i                 ../../lib/libGL.so
mglGetFloatv                        ../../lib/libGLU.so
mglWindowPos3svMESA                 ../../lib/libGL.so
mglWindowPos4dvMESA                 ../../lib/libGL.so
mglGetBufferPointerv                ../../lib/libGL.so
mglGetTrackMatrixivNV               ../../lib/libGL.so
...
ld: fatal: Symbol referencing errors. No output written to arbfplight
collect2: ld returned 1 exit status
make[3]: *** [arbfplight] Error 1
make[3]: Leaving directory `/export/home/egger/src/mesa/Mesa-6.5/progs/demos'
make[2]: *** [subdirs] Error 1
make[2]: Leaving directory `/export/home/egger/src/mesa/Mesa-6.5/progs'
make[1]: *** [default] Error 1
make[1]: Leaving directory `/export/home/egger/src/mesa/Mesa-6.5'
make: *** [sunos5-gcc] Error 2

Probably that won't work with CVS but ok I test it:
make[2]: Entering directory `/export/home/egger/src/mesa/cvs/Mesa/progs'
Making programs for sunos5-gcc
make[3]: Entering directory `/export/home/egger/src/mesa/cvs/Mesa/progs/demos'
cp ../../progs/util/readtex.c .
cp ../../progs/util/readtex.h .
gcc -c -I../../include -Wall -O3 -g -fomit-frame-pointer -pipe -fPIC 
-D_REENTRANT -DUSE_XSHM -DUSE_MGL_NAMESPACE -  DUSE_SPARC_ASM -std=c99
-ffast-math -I/usr/openwin/include readtex.c
gcc -I../../include -Wall -O3 -g -fomit-frame-pointer -pipe -fPIC  -D_REENTRANT
-DUSE_XSHM -DUSE_MGL_NAMESPACE -DUS  E_SPARC_ASM -std=c99 -ffast-math
-I/usr/openwin/include arbfplight.c readtex.o -L../../lib -lX11 -lglut -lGLU
-lGL   -lm -o arbfplight
Undefined                       first referenced
 symbol                             in file
mglGetMinmax                        ../../lib/libGL.so
mglNormal3fv                        ../../lib/libglut.so
mglNormal3dv                        ../../lib/libGL.so
mglNormal3bv                        ../../lib/libGL.so
mglNormal3iv                        ../../lib/libGL.so
mglNormal3sv                        ../../lib/libGL.so
mglSecondaryColor3s                 ../../lib/libGL.so
mglSecondaryColor3b                 ../../lib/libGL.so
mglSecondaryColor3d                 ../../lib/libGL.so
mglSecondaryColor3f                 ../../lib/libGL.so
mglSecondaryColor3i                 ../../lib/libGL.so
mglGetFloatv                        ../../lib/libGLU.so
mglWindowPos3svMESA                 ../../lib/libGL.so
...
ld: fatal: Symbol referencing errors. No output written to arbfplight
collect2: ld returned 1 exit status
make[3]: *** [arbfplight] Error 1
make[3]: Leaving directory `/export/home/egger/src/mesa/cvs/Mesa/progs/demos'
make[2]: *** [subdirs] Error 1
make[2]: Leaving directory `/export/home/egger/src/mesa/cvs/Mesa/progs'
make[1]: *** [default] Error 1
make[1]: Leaving directory `/export/home/egger/src/mesa/cvs/Mesa'
make: *** [sunos5-gcc] Error 2