Enable CMake-based build for Borland and Watcom compilers

Enable CMake-based build for Borland and Watcom compilers

Issue #105 (bdwgc).

* CMakeLists.txt [BORLAND] (add_compile_options): Specify /a4 and
/w /w-pro /w-aus /w-par /w-ccc /w-inl /w-rch; add comment.
* CMakeLists.txt [WATCOM] (add_compile_options): Specify /zp4 and /wx.
* CMakeLists.txt [enable_werror && BORLAND] (add_compile_options):
Specify /w!.
* CMakeLists.txt [enable_werror && WATCOM] (add_compile_options):
Specify /we.
* CMakeLists.txt [!enable_single_obj_compilation && !BUILD_SHARED_LIBS
&& BORLAND] (add_compile_options): Specify /w-use; add comment.
* CMakeLists.txt [build_tests && WATCOM] (gctest): Specify /wcd=13
/wcd=201 /wcd=367 /wcd=368 /wcd=726 target compile options; add comment.
* doc/README.win32 (Watcom compiler): Mention that OpenWatcom 2.0 is
tested on; remove note that cord is not ported; add note about the
new way to build the collector using CMake script.