Add Wextra warnings and exclude some

Author: Girgias

Zend/Zend.m4

@@ -221,7 +221,7 @@ else
   AC_DEFINE(ZEND_DEBUG,0,[ ])
 fi
 
-test -n "$GCC" && CFLAGS="$CFLAGS -Wall -Wno-strict-aliasing"
+test -n "$GCC" && CFLAGS="$CFLAGS -Wall -Wno-strict-aliasing -Wextra -Wno-clobbered -Wno-implicit-fallthrough -Wno-unused-parameter -Wno-sign-compare -Wno-missing-field-initializers"
 test -n "$DEBUG_CFLAGS" && CFLAGS="$CFLAGS $DEBUG_CFLAGS"
 
 if test "$ZEND_ZTS" = "yes"; then