snprintf: fix some compile time checks for MSVC
snprintf: fix some compile time checks for MSVC

MSVC with cmake results in a few compile time checks
in snprintf.c not being compilable. Changing the statements
such that MSVC can understand them.

git-svn-id: d023f1085a36f7a677188d00334e37d38ffecf51@965 64e312b2-a51f-0410-8e61-82d0ca0eb02a

krichter722/check,9fcc/check,brarcher/check,krichter722/check,krichter722/check,brarcher/check,krichter722/check,brarcher/check,9fcc/check,brarcher/check,9fcc/check,krichter722/check,libcheck/check,9fcc/check,libcheck/check,9fcc/check,brarcher/check,libcheck/check,libcheck/check,libcheck/check