The global ::LockFile() function is used in a single place, but it's in
common.h, so visible to all files.
The GetKicadLockFilePath function is used in only two places, and one of
them is LockFile.
This commit puts them both in a separate header, so they're only visible
to code using them.
The implementation of GetKicadLockFilePath is moved to lockfile.cpp,
where LockFile already was.
Also removed a (large) handful of wxT macros, which aren't needed any
more and make code less readable.
John Beard