(vhdl-add-index-menu): reverse order in imenu-generic-expression.

(vhdl-add-index-menu): reverse order in imenu-generic-expression.
(vhdl-template-assert, vhdl-block, vhdl-configuration-spec)
(vhdl-elsif, vhdl-generate, vhdl-if, vhdl-map)
(vhdl-selected-signal-assignment, vhdl-use, vhdl-while-loop)
(vhdl-get-port, vhdl-get-generic): Replace (undo 0) by (undo).
(vhdl-when): Fix indentation problem.
(vhdl-outer-space): Add "_" to syntax table for expand-abbrev.
(vhdl-get-port, vhdl-get-generic): Bug fix in template.
(vhdl-hooked-abbrev): Bug fix in hooked abbrev.