[release] Update version post release to 0.9.4+

src/Makefile.housekeeping

@@ -12,7 +12,7 @@ CLEANUP	:= $(BIN)/*.* # *.* to avoid catching the "CVS" directory
 VERSION_MAJOR	= 0
 VERSION_MINOR	= 9
 VERSION_PATCH	= 4
-EXTRAVERSION	=
+EXTRAVERSION	= +
 MM_VERSION	= $(VERSION_MAJOR).$(VERSION_MINOR)
 VERSION		= $(MM_VERSION).$(VERSION_PATCH)$(EXTRAVERSION)
 CFLAGS		+= -DVERSION_MAJOR=$(VERSION_MAJOR) \