Define HAS_ALTIVEC on OS X (should do a proper test here, in case we are run on Darwin/x86, but for now I am lazy)

svn-id: r11503

configure

@@ -365,6 +365,8 @@ case $hosttype in
 	Darwin)
 		DEFINES="$DEFINES -DUNIX -DMACOSX"
 		LIBS="$LIBS -framework QuickTime -framework AudioUnit"
+		# TODO: Add proper check for Altivec support in the compiler...
+		DEFINES="$DEFINES -DHAS_ALTIVEC"
 		CXXFLAGS="$CXXFLAGS -faltivec"
 		;;
 	MINGW32*)
@@ -614,8 +616,8 @@ cat > config.mak << EOF
 # -------- Generated by configure -----------
 
 CXX := $CXX
-CXXFLAGS := $CXXFLAGS
-LIBS := $LIBS
+CXXFLAGS += $CXXFLAGS
+LIBS += $LIBS
 RANLIB := $_ranlib
 BACKEND := $_backend
 MODULES += $MODULES