Ticket 49068 - 1.3.5 use std c99
Bug Description: When we enabled the cve fix for constant time password comp,
we included code that relied on a c99 feature. But we did not add the c99 flags
to configure.ac. This has broken some distributions ports.
Fix Description: Add the AC_PROG_CC_STDC to configure.ac, and run autoreconf.
Review by: mreynolds (thanks!)