[pacman-dev] Version bounds for IgnorePkg

[Daniel Schoepe]

Hi,

A common situation for me is to ignore a specific known-to-be-buggy version of
a package with a fix being available in the next upcoming version. I think it
would be a good idea to allow ignoring a specific package version. The
following patch implements this functionality.

Since this is my first contribution to pacman / alpm, I'm not sure if
I followed the coding style. A few notes on the implementation:

- As discussed when I brought this up a while back, only equality constraints
  are supported, since the other types of bounds would have unclear semantics.
- This is checked for by pacman and libalpm assumes that only such IgnorePkg
  entries are added. I'm not sure if this check should rather be handled by
  libalpm instead.
- alpm_handle_t.ignorepkg is now a list of alpm_depend_t structures, not
  strings. This required some more widespread changes to avoid duplicating the
  code that handles assumeinstalled entries.

Comments and suggestions are of course appreciated.

Best regards,
Daniel