* configure.ac: Fix PR gdb/15414
	Fix FTBFS on mingw32 GCC 4.8.0 - -Wformat-* cannot be used when
	-Wno-format is also present - this causes a warning in GCC 4.8.0 (does
	not happen in earlier versions), which is treated as error.
	
	* sim/common/acinclude.m4: Likewise