Add -ansi flag when building with gcc

BUILD/SETUP.sh:
  Add -ansi flag, make gcc not allow "C++ comments in C"

BUILD/SETUP.sh

@@ -43,7 +43,7 @@ AM_MAKEFLAGS="-j 4"
 # The following warning flag will give too many warnings:
 # -Wshadow -Wunused  -Winline (The later isn't usable in C++ as
 # __attribute()__ doesn't work with gnu C++)
-global_warnings="-Wimplicit -Wreturn-type -Wswitch -Wtrigraphs -Wcomment -W -Wchar-subscripts -Wformat -Wparentheses -Wsign-compare -Wwrite-strings"
+global_warnings="-Wimplicit -Wreturn-type -Wswitch -Wtrigraphs -Wcomment -W -Wchar-subscripts -Wformat -Wparentheses -Wsign-compare -Wwrite-strings -ansi"
 #debug_extra_warnings="-Wuninitialized"
 c_warnings="$global_warnings -Wunused"
 cxx_warnings="$global_warnings -Woverloaded-virtual -Wsign-promo -Wreorder -Wctor-dtor-privacy -Wnon-virtual-dtor"