Include CMakeParseArguments in Qt5LinguistToolsMacros.cmake

This is shipped with CMake 2.8.3, which is the minimum version of
CMake required anyway.

Task-number: QTBUG-38375
Change-Id: I48c155f9532fafe2b91544a93cf489f238f0b9d9
Reviewed-by: Volker Krause <volker.krause@kdab.com>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
CMake: Check that executables in the linguist package exist before use.

Change-Id: Ifaaff157a836e3ebfb94b563631b65a226ed0d8c
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
CMake: Add a lconvert IMPORTED target.

Task-number: QTBUG-37937
Change-Id: I3d389f8a96b04b8d94d13990d55a88bb5637a1e3
Reviewed-by: Volker Krause <volker.krause@kdab.com>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
CMake: Add an IMPORTED target for qcollectiongenerator.

This makes it easier to generate assistant documentation with
Sphinx, for example.

Change-Id: Idb45ec47f3c2bcf8a6df313380abf71a4c5a7da5
Reviewed-by: Volker Krause <volker.krause@kdab.com>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>