make: avoid interactive query due to UnxUtils mv.exe invocation

It made a user intervention necessary:
mv: replace `generated/primitive.c', overriding mode 0666?

Replace the usage of 'mv' by 'cp' + 'rm'.
'mv -f' would have been sufficient, but the file is created in lowercase then.

This was the only place where 'mv' has been used.
SDL: ignore SDL_TEXTEDITING event

Noticed during startup when running on Windows 7.
make: fix grc invocation when MLA path contains spaces

In this case C:\Program Files (x86)\...