[Rpcemu] Another little patch for macOS

Rounding off the work I've been making doing for macOS X, is the attached patch.

• VERSION is now defined in the QT .pro file, rather than in rpcemu.h
• The Mac application info.plist uses this for the correct application version
• The Mac application bundle identifier is properly composed using qmake variables, leading to a different identifier for the recompiler vs interpreter versions; this allows both of them to be added to Security & Privacy settings as independent entities.

The line numbers in the patch are for a set of sources already patched with Timothy Coltman's V4 Mac patch, but would probably work successfully in unpatched source too using just the diff context. While this small change set is mostly Mac-focused, I do think having the version specified in the project file is the right thing generally and it might be a useful addition to the main source tree.

--   Andrew Hodgkinson  RISC OS Open Limited  http://www.riscosopen.org/