Replace USE_GCC=4.6+ and USE_GCC=4.4+ by USE_GCC=yes.

Right now this is a noop in the former case and a noop in the latter
case unless lang/gcc44 has been installed explicitly.

This puts a bit more emphasis on standardizing on a canonical version
"current" GCC and makes it easier to update that canonical version
by changing the default in Mk/bsd.gcc.mk and updating the lang/gcc port.

That is, USE_GCC=yes means "use a decent/modern version of GCC" without
having to worry about details.

Approved by:	portmgr (bdrewery)

java/classpath/Makefile

@@ -141,7 +141,7 @@ JAVA?=			${LOCALBASE}/bootstrap-openjdk/bin/java
 JAVAC?=			${LOCALBASE}/bootstrap-openjdk/bin/javac
 .else
 USE_BINUTILS=		yes
-USE_GCC=		4.6+
+USE_GCC=		yes
 GCC_SUFX=		${_USE_GCC:S/.//}
 JAR?=			${LOCALBASE}/bin/gjar${GCC_SUFX}
 JAVA?=			${LOCALBASE}/bin/gij${GCC_SUFX}