This is an attempt to make it work with released gdb 7.0. It uses some
ugly workarounds to compensate for the missing gdb.Block and gdb.Symbol
structures.

 * Remove one layer of layout.

Reviewed-by: dt

Make the diff-base directory a property of VCSBaseEditor and use
everywhere.

Task-number: QTCREATORBUG-74

The search results window assumed the files were searched in sorted
order, which is not always the case especially since "find usages" can
now operate in several threads.

This change makes sure that the list of files in the search results is
always sorted, using a binary search to find the right index to insert
new files.

Reviewed-by: con

It used to be hidden on the Display settings page.

Task-number: QTCREATORBUG-135

arrays

no point in re-parsing them over and over during the scan of a bigger
project ...

shaves off another 20% of the loading time of Qt 4.6.

there is no point in throwing away and re-recreating invariant data over
and over ...

shaves off ~15% of the load time of Qt 4.6.

makes forward delcs in headers possible

findProFileFor(), buildDir() and createProFileReader() make sense only
in relation with an actual pro file anyway, so move them there.

this is probably just as fast (still two allocs per insert), but it is
definitely more elegant.

Remove logic handling several repositories.

Make use of VCS base class.

Fixes:
- Cannot diff a file that does not belong to a project
- Cannot commit when a temporary diff/log view is open
  due to the current file pointing to a temporary directory
- git's project-related actions not passing the correct
  relative path.

Implementation:
- Centralize code to listen for Qt Creator's relevant state changes
  in VCSBasePlugin, dispatching the changes to the instances affected.
  (avoiding multiple invocations of searches/QFileInfo on current).
- Do the same for the corelistener catching closing SubmitEditors.
- Introduce VCSBasePluginState representing the relevant state
  (current file/project).
- Call git with working directory set and relative arguments
- Remove setEnabled/isEnabled() logic of IVersionControl
- Pass toplevel from VCSManager to avoid duplicate searches.

 * Remove unnecessary headers.
 * Remove hardly used variables.
 * QTC_ASSERT before using a pointer which might be 0.

Reviewed-by: dt