The source project of this merge request has been removed.
Various parts of Xfce, and libraries used by Xfce, already use C99 features. Therefore it is reasonable to expect the availibility of a capable compiler. Current GCC releases silently default to newer C standards, starting with gcc-5 which defaults to C11.
Replace AC_PROG_CC with AC_PROG_CC_C99 to switch the discovered, or specified, compiler to C99.
Signed-off-by: Olaf Hering olaf@aepfle.de