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.
    
    https://fedorahosted.org/389/ticket/49068
    
    Author: wibrown
    
    Review by: mreynolds (thanks!)