A recent commit added the file src/stc/PlatWXcocoa.mm needed for wxSTC
with the cocoa port. This commit modifies the build system files to
use this new file when it is needed.
The auto-generated header causes undefined members and identifiers in the
standard c++ headers when using clang on macOS or Windows.
Do not disable precompiled headers entirely but use the main Scintilla
header as prefix header so there is at least a small speedup.
Add CMake build system for libraries, tests and samples
update_files.py converts build/files into CMake format.
build/update-setup-h has been modified to update build/cmake/setup.h.in.