Add support for -v option on OpenBSD. Fixes #61.

- Functions to implement verbosity (without locale support) on basic actions, and
- Handle verbosity on OpenBSD: ```cp```, ```ln```, ```rm``` and ```mv``` doesn't accept the -v option.

Issue:
Function ```rm_v``` must be called with one option and the file to delete. The rest of functions only accepts two parameters.
Basic actions (cp, ln, rm and mv) may be more secure to use with a function wrapper instead of ```$CP```, ```$LN```, ```$RM``` and ```$MV``` directly (TODO).

Thanks
Javier López