alloca implicitly declared on Solaris11 x86
When compiling c/_cffi_backend.c on Solaris 11 x86, gcc complains that alloca is implicitly declared. Simply adding
#include <allocal.h> to the file solves this issue.
If you need to put this into an
#ifdef section you might be able to use
__sun which AFAIK is defined by both gcc and SunStudio.