Test-suite makefile fixes for Windows

Remove $(realpath ) which is no good for Windows executables running
under Cygwin's make
CCache: always generate docs in source directory
Distclean Tools/javascript
Fully clean Go test-suite
Fix Javascript examples so that "make clean" works properly with node

- Need to copy example.cxx to build directory so that build products
  end up in the right place; use a gyp command expansion to do so
Fully clean Javascript test-suite with jsc and v8
Fully clean PHP test-suite
Fully clean Python examples and test-suite
Set SRCDIR when calling test-suite clean targets, in case it's needed
Add check-maintainer-clean target: fails if files are missed by maintainer-clean
check-maintainer-clean: print message only for out-of-source builds