Eliminate some nested repetitions in regexps

Eliminate some nested repetitions in regexps

Nested repetitions such as (A*)* potentially take exponential time but
can usually be rewritten in a faster and more readable way without
much trouble.  These were all found by Relint.

* lisp/obsolete/terminal.el (te-parse-program-and-args):
* lisp/org/org.el (org-make-tags-matcher):
Apply the transform (A+B*)+ -> A(A|B)*

* lisp/textmodes/fill.el (adaptive-fill-regexp):
Apply the transform A*(B+A*)* -> (A|B)*

* lisp/progmodes/idlw-shell.el (idlwave-shell-filter):
Find the last newline or CR in a more direct way.

* lisp/progmodes/vhdl-mode.el (vhdl-port-copy, vhdl-subprog-copy):
Trim trailing whitespace from a string in a more direct way.
All-whitespace strings are left unchanged as before.