6079 libdisasm doesn't enable C99MODE properly

@@ -31,7 +31,5 @@
 
 INSTALL_DEPS_library =          $(ROOTLINKS) $(ROOTLINT) $(ROOTLIBS)
 INSTALL_DEPS_standalone =       $(ROOTLIBS)
 
 include ../Makefile.targ
-
-C99MODE = $(C99_ENABLE)