Xrender.h should not be #included without including <X11/Xlib.h> first. Otherwise, XID remains undefined on Solaris 10, causing the test to fail:

configure:22124: checking X11/extensions/Xrender.h usability
configure:22124: gcc -c -g -O2 -D_POSIX_PTHREAD_SEMANTICS    -I/usr/openwin/include conftest.c >&5
In file included from /usr/openwin/include/X11/extensions/Xrender.h:28:0,
                 from conftest.c:115:
/usr/openwin/include/X11/extensions/render.h:29:1: error: unknown type name 'XID'
/usr/openwin/include/X11/extensions/render.h:30:1: error: unknown type name 'XID'
/usr/openwin/include/X11/extensions/render.h:31:1: error: unknown type name 'XID'
/usr/openwin/include/X11/extensions/render.h:32:1: error: unknown type name 'XID'
configure:22124: $? = 1
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME "cairo"
| #define PACKAGE_TARNAME "cairo"
| #define PACKAGE_VERSION "1.12.8"
| #define PACKAGE_STRING "cairo 1.12.8"
| #define PACKAGE_BUGREPORT "http://bugs.freedesktop.org/enter_bug.cgi?product=cairo"
| #define PACKAGE_URL "http://cairographics.org/"
| #define STDC_HEADERS 1
| #define HAVE_SYS_TYPES_H 1
| #define HAVE_SYS_STAT_H 1
| #define HAVE_STDLIB_H 1
| #define HAVE_STRING_H 1
| #define HAVE_MEMORY_H 1
| #define HAVE_STRINGS_H 1
| #define HAVE_INTTYPES_H 1
| #define HAVE_STDINT_H 1
| #define HAVE_UNISTD_H 1
| #define __EXTENSIONS__ 1
| #define _ALL_SOURCE 1
| #define _GNU_SOURCE 1
| #define _POSIX_PTHREAD_SEMANTICS 1
| #define _TANDEM_SOURCE 1
| #define HAVE_DLFCN_H 1
| #define LT_OBJDIR ".libs/"
| #define _FILE_OFFSET_BITS 64
| #define WARN_UNUSED_RESULT __attribute__((__warn_unused_result__))
| #define HAVE_INTEL_ATOMIC_PRIMITIVES 1
| #define SIZEOF_VOID_P 4
| #define SIZEOF_INT 4
| #define SIZEOF_LONG 4
| #define SIZEOF_LONG_LONG 8
| #define SIZEOF_SIZE_T 4
| #define HAVE_LIBRT 1
| #define HAVE_BUILTIN_RETURN_ADDRESS 1
| #define HAVE_STDINT_H 1
| #define HAVE_INTTYPES_H 1
| #define HAVE_SYS_INT_TYPES_H 1
| #define HAVE_UINT64_T 1
| #define HAVE_FCNTL_H 1
| #define HAVE_UNISTD_H 1
| #define HAVE_SIGNAL_H 1
| #define HAVE_SYS_STAT_H 1
| #define HAVE_SYS_SOCKET_H 1
| #define HAVE_SYS_POLL_H 1
| #define HAVE_SYS_UN_H 1
| #define HAVE_ALARM 1
| #define HAVE_SCHED_H 1
| #define HAVE_SYS_MMAN_H 1
| #define HAVE_MMAP 1
| #define HAVE_TIME_H 1
| #define HAVE_CLOCK_GETTIME 1
| #define HAVE_FECLEAREXCEPT 1
| #define HAVE_LIBGEN_H 1
| #define HAVE_SIGNAL_H 1
| #define HAVE_SETJMP_H 1
| #define HAVE_FENV_H 1
| #define HAVE_SYS_WAIT_H 1
| #define HAVE_CTIME_R 1
| #define HAVE_DRAND48 1
| #define HAVE_FLOCKFILE 1
| #define HAVE_FUNLOCKFILE 1
| #define HAVE_LINK 1
| #define HAVE_SYS_STAT_H 1
| #define HAVE_MKDIR 2
| #define HAVE_FORK 1
| #define HAVE_WAITPID 1
| #define HAVE_RAISE 1
| #undef PACKAGE_VERSION
| #undef PACKAGE_STRING
| #undef PACKAGE_NAME
| #undef PACKAGE_TARNAME
| #define PACKAGE_VERSION USE_cairo_version_OR_cairo_version_string_INSTEAD
| #define PACKAGE_STRING USE_cairo_version_OR_cairo_version_string_INSTEAD
| #define PACKAGE_NAME USE_cairo_INSTEAD
| #define PACKAGE_TARNAME USE_cairo_INSTEAD
| #define HAVE_ZLIB 1
| #define HAVE_DLFCN_H 1
| #define CAIRO_HAS_DLSYM 1
| #define HAVE_X11_EXTENSIONS_XSHM_H 1
| #define HAVE_X11_EXTENSIONS_SHMSTR_H 1
| /* end confdefs.h.  */
| #include <stdio.h>
| #ifdef HAVE_SYS_TYPES_H
| # include <sys/types.h>
| #endif
| #ifdef HAVE_SYS_STAT_H
| # include <sys/stat.h>
| #endif
| #ifdef STDC_HEADERS
| # include <stdlib.h>
| # include <stddef.h>
| #else
| # ifdef HAVE_STDLIB_H
| #  include <stdlib.h>
| # endif
| #endif
| #ifdef HAVE_STRING_H
| # if !defined STDC_HEADERS && defined HAVE_MEMORY_H
| #  include <memory.h>
| # endif
| # include <string.h>
| #endif
| #ifdef HAVE_STRINGS_H
| # include <strings.h>
| #endif
| #ifdef HAVE_INTTYPES_H
| # include <inttypes.h>
| #endif
| #ifdef HAVE_STDINT_H
| # include <stdint.h>
| #endif
| #ifdef HAVE_UNISTD_H
| # include <unistd.h>
| #endif
| #include <X11/extensions/Xrender.h>

On Solaris 10, <X11/extensions/Xrender.h> is located in
   /usr/openwin/share/include/X11/extensions/Xrender.h
which has as first include
   #include <X11/extensions/render.h>
which in turn loads /usr/openwin/share/include/X11/extensions/render.h. These
are the very first lines of it:

typedef XID             Glyph;
typedef XID             GlyphSet;
typedef XID             Picture;
typedef XID             PictFormat;

But XID has not been defined at that point as unfortunately neither Xrender.h
nor render.h as shipped under Solaris include <X11/Xlib.h> first. Both files
are part of the Solaris 10 package SUNWxwinc in the version
   6.6.2.7400,REV=0.2004.12.15

A workaround is to specify
   xlib_CFLAGS="-include /usr/openwin/include/X11/X.h"
to configure.