Even though that pragma is standard C99, MSVC doesn't understand it.
An issue has been opened, and this commit should be reverted when/if
they fix it:
https://connect.microsoft.com/VisualStudio/feedback/details/
1009089/unhandled-standard-macros
AS_IF([test "${ac_cv_c_fast_math}" = "no"], [VLC_RESTORE_FLAGS])
AH_BOTTOM([
#ifndef __FAST_MATH__
-# pragma STDC FENV_ACCESS OFF
-# pragma STDC FP_CONTRACT ON
+# ifndef _MSC_VER
+# pragma STDC FENV_ACCESS OFF
+# pragma STDC FP_CONTRACT ON
+# else
+# pragma fenv_access(off)
+# pragma fp_contract(on)
+# endif
#endif
])