Hello,

While developing some features for `vhdl-ext` MELPA package (
https://github.com/gmlarumbe/vhdl-ext) I believe I have come across a bug
in `vhdl-mode` function `vhdl-corresponding-begin`.

Inside the cond block, for the "end component" condition, it seems that the
enclosing parentheses to set capture group 1 in the `looking-at` string
argument are missing.

I attach a simple patch that fixes it.

Thanks!

Gonzalo