Fix crashes in QtHelp when too many connections are made

Fixes a crash when Qt Creator was registering a large number of .qch
files on first startup: In this case the limit of 1000 connections
within one session will overflow, resulting in conflicting connection
names and crashes later on.

Remove this limitation by keeping separate counters per connection name,
and also not wrapping around after 1000.

It's not clear where the 1000 connection limit stems from: The offending
lines predate the first git import of Qt 4.

Task-number: QTBUG-36480
Change-Id: If00276652644efa854a75407d00ba01069bde02a
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>
Update changelog for 5.2.1

Change-Id: I16ff3a410898563857b70d467f6ba8599c722ce6
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Assistant: Load all applicationIcon pixmaps.

Qt Assistant, when used as a custom help viewer, would not load all
sizes of the application icon specified in the .qhcp file. Now
application icons look good everywhere, provided the files contain
multiple icons of various sizes.

Task-number: QTBUG-28267

Change-Id: I362e2feafa7944b0ad25627fb2fcea1b90af4e53
Reviewed-by: Thorbjørn Lund Martsum <tmartsum@gmail.com>
Merge remote-tracking branch 'origin/release' into stable

Change-Id: I6d8fce7daab4dcfc9ffc93543dd0a1337a3f3c9d