A little cleanup
Implemented extmod options print function.
Added extmod_has_* functions.

Used for checking properties of extmod structure without direct field
call.
Rename long and short extmod description fields.

desc      -> desc_short
desc_long -> desc
Uninline some functions.

Also unneeded in public header function was hidden into private
header.
Corrected captions for 'help' and 'version' special extopts.
Fix version extraction for multidigital numbers.
Added global variable 'extmod' pointing to currently executed module
structure.

If no module is executed than value of extmod is 0.