* lib/verify.h (_GL_VERIFY): Port MSVC hack back to C99.
Problem found when testing bleeding-edge gzip on IBM XL C for AIX,
V12.1 (5765-J02, 5725-C72), which complained ‘"malloca.c", line
42.56: 1506-041 (E) The invocation of macro _Static_assert
contains fewer arguments than are required by the macro
definition.’ This diagnostic is valid because C99 requires
that if you #define _Static_assert(R, ...) you must call
_Static_assert with at least two arguments. I found a similar
problem with Sun C 5.9 SunOS_sparc Patch 124867-12 2009/11/22.