ffap-include-start

M-x ffap normally only recognises an include like

    #include <foo.h>

when point is on the filename part.  This spot of code lets it work when
point in the "#include" part.  The following forms are supported,

    #include <foo.h>       C language
    #include "foo.h"       C language
    @include "foo.awk"     GNU Awk
    include foo.make       GNU Make
    include "foo.rc"       Gtk RC file

You can always move point to the filename and M-x ffap from there, but
it's handy to have it work from the start of the line too, especially
when just browsing rather than editing.

GNU Make can do a multiple-file include.  The first filename is offered
when point is on the include.  Move point to the second name to get that.

    include foo.make bar.make

This code works with ffap-makefile-vars.el.  If you load that package
then a GNU Make include can have variables to expand,

    include $(HOME)/mystuff/foo.make