shorten descriptions, mostly refer to the separate descriptions

... and fixed mancheck to ignore obsolete options

Now all current options have their own man pages.

To be further discussed, debated and edited

This is consistent with the existing obsolete error code naming
convention.

... from the CINIT() enum

We now provide the "real" names in the CINIT() macro setup for CURLOPT_*
symbols, and we provide backwards compatibility defines for the old
symbols as defines instead of vice versa.

This allows us to better use the CINIT() list to check for existing and
current option names.