Watcom: Fix creation of DLLs without any exported symbols

Create each DLL import library by passing "option implib=..." to the
linker for its SHARED library.  This works even when there are no
symbols to be exported.  Leave the option out for MODULE libraries
because we do not need an import library for them.  For executables,
retain the separate invocation of wlib because we want an import
library only when the ENABLE_EXPORTS property is set, and in that
case the project should provide symbols.

Suggested-by: J Decker <d3ck0r@gmail.com>
FindRuby: Add support for Ruby 2.0 and 2.1

The most significant change since Ruby 1.9 is the changed path of
config.h, from RbConfig::CONFIG['rubyhdrdir'] to
RbConfig::CONFIG['rubyarchhdrdir'].
Help: Add FindRuby-2 topic release notes
Remove compatibility CTest code.
Watcom: Fix static library name quoting for wlib

Use double-quotes instead of single-quotes around the static library
target name in 'wlib' invocations.
CPackWIX: Allow Windows Installer property customization
CPackWIX: support installation of empty directories
FindPythonLibs: Find consistent Python interp, headers, libs (#13794)

When possible, get consistent version of the Python interpreter, headers path,
and library.

Now find_package(PythonLibs) internally calls find_package(PythonInterp
QUIET) and uses the resulting PYTHON_VERSION_MAJOR and
PYTHON_VERSION_MINOR to prefer these versions when looking for the
header path and library.  The Python_ADDITIONAL_VERSIONS variable has
priority over the interpreter version.

Co-Author: Adam Wolf
Co-Author: Gert Wollny <gw.fossdev@gmail.com>
Merge topic 'different-python-header-libs-exe-0013794'

3816cd2d FindPythonLibs: Find consistent Python interp, headers, libs (#13794)
Merge topic 'watcom-dll-no-symbols'

00503d38 Watcom: Fix creation of DLLs without any exported symbols
Merge topic 'watcom-wlib-quoting'

5c5be193 Watcom: Fix static library name quoting for wlib
Merge topic 'remove-compatibility-ctest'

4b67c4b9 Remove compatibility CTest code.
Merge topic 'FindRuby-2'

57abfeaa Help: Add FindRuby-2 topic release notes
165f6430 FindRuby: Add support for Ruby 2.0 and 2.1
Merge topic 'wix-additions'

642fa25d CPackWIX: support installation of empty directories
378eb5b7 CPackWIX: Allow Windows Installer property customization
add_definitions: Don't document genex support.

This command does not support generator expressions. The documentation
was mistakenly extended to claim it in commit v3.0.0-rc1~60^2~3 (Help: Mark
up the buildsystem commands documentation, 2014-02-03).
CMP0043: Document old and new interfaces for setting directory property.
Merge topic 'CMP0043-dir-prop'

38df26bc CMP0043: Document old and new interfaces for setting directory property.
Merge topic 'add_definitions-no-genex'

1a9316a8 add_definitions: Don't document genex support.