Run piglit arb_multisample-pushpop on softpipe or llvmpipe.

$ ./bin/arb_multisample-pushpop
sanity test test:
Segmentation fault (core dumped)

(gdb) bt
#0  0x00007f3cf7d83a67 in _mesa_meta_in_progress (ctx=ctx@entry=0x1ed86e0)
    at ../../../src/mesa/drivers/common/meta.c:1085
#1  0x00007f3cf832c2b8 in _mesa_set_enable (ctx=0x1ed86e0, cap=32925, 
    state=<optimized out>) at ../../src/mesa/main/enable.c:771
#2  0x00007f3cfbd3438f in stub_glEnable (cap=32925)
    at piglit/tests/util/generated_dispatch.c:5645
#3  0x0000000000400ee9 in set_enable_bits (val=true)
    at piglit/tests/spec/arb_multisample/pushpop.c:97
#4  0x00000000004010d0 in pushpop (bit=0, test=0x401483 "sanity test", 
    affects_enabled=true, affects_other=true)
    at piglit/tests/spec/arb_multisample/pushpop.c:156
#5  0x00000000004011da in piglit_init (argc=1, argv=0x7ffffa04b478)
    at piglit/tests/spec/arb_multisample/pushpop.c:192
#6  0x00007f3cfbd2618c in piglit_gl_test_run (argc=1, argv=0x7ffffa04b478, 
    info=0x7ffffa04b370) at piglit/tests/util/piglit-framework.c:133
#7  0x0000000000400d61 in main (argc=1, argv=0x7ffffa04b478)
    at piglit/tests/spec/arb_multisample/pushpop.c:54
(gdb) frame 0
#0  0x00007f3cf7d83a67 in _mesa_meta_in_progress (ctx=ctx@entry=0x1ed86e0)
    at ../../../src/mesa/drivers/common/meta.c:1085
1085	   return ctx->Meta->SaveStackDepth != 0;
(gdb) print ctx->Meta
$1 = (struct gl_meta_state *) 0x0


d638da23d2ec2e9c52655b1ea138249e7f8bcccb is the first bad commit
commit d638da23d2ec2e9c52655b1ea138249e7f8bcccb
Author: Paul Berry <stereotype441@gmail.com>
Date:   Wed Aug 8 11:56:33 2012 -0700

    meta: Don't stray outside the confines of the API specified in the context
    
    Signed-off-by: Paul Berry <stereotype441@gmail.com>
    Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>

:040000 040000 fbabd4b3b67869f18ba255cf3f53e3955163313e 1bee307142209333210a019471ffcac041e84ff9 M	src
bisect run success