build: remove D__STDC_FORMAT_MACROS from CPPFLAGS

This was used to expose additional formatting macros in glibs / std
libs. However this is no-longer required now that we require glibc
2.18+.

See https://sourceware.org/bugzilla/show_bug.cgi?id=15366.

configure.ac

@@ -581,7 +581,7 @@ CXXFLAGS="$TEMP_CXXFLAGS"
 
 fi
 
-CPPFLAGS="$CPPFLAGS -DHAVE_BUILD_INFO -D__STDC_FORMAT_MACROS"
+CPPFLAGS="$CPPFLAGS -DHAVE_BUILD_INFO"
 
 AC_ARG_WITH([utils],
   [AS_HELP_STRING([--with-utils],