makedepend is rather early in the distro bootstrap chain, so it shouldn't pull in anything it doesn't really need.
xproto is only pulled in for two macros which we can just as easily provide ourselves.
I'm not entirely sure about
X_NOT_POSIX, that seems to be the only other use of this?
Makefile.am:AM_CPPFLAGS += $(X_CFLAGS)coming from?