carve out qmake project parser from lupdate & lrelease

the built-in qmake project parser in the linguist tools is a somewhat insane idea - among other things, it makes sharing the tools between builds hard (because it uses a specific qmake to figure out the configuration, and that is bound to the build).
it also puts alternative build tools at a disadvantage, as the command line is not powerful enough to convey the project structure sufficiently precisely.

therefore, the project parser should be extracted.
the new tools lupdate-pro and lrelease-pro should do the project evaluation, and call the "proper" tools correspondingly.
the original tools should call out to the -pro versions for compatibility; that mode should be deprecated.