Expunge "allow" + infinitive from source and doc, part 2.

Expunge "allow" + infinitive from source and doc, part 2.

Do the same for "permit", "enable", "prevent", and (where appropriate)
"require".

doc/misc/reftex.texi:
doc/misc/url.texi:
lib/get-permissions.c:
lib/strftime.c:
lisp/org/org-element.el:
lisp/org/org-mobile.el:
lisp/textmodes/reftex-vars.el:
src/bidi.c:
src/emacs.c:
src/xdisp.c:
test/etags/c-src/emacs/src/lisp.h:

Expunge the likes of "This allows to do something" from the above files.