Pixman no-longer builds with gcc v4.6.x

[darxus at chaosreigns.com]

https://bugs.freedesktop.org/show_bug.cgi?id=55630

Workarounds:
1) Build with the last good commit:
   7a9c2d586b2349b5e17966a96d7fe8c390abb75a
2) Upgrade gcc.
3) Build with clang instead of gcc, although that may have other problems.
   '"export CC=clang" before autogen.sh/configure'
   'it's best to run "make check" to see whether you get healthy build'

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