suggested by PEP 291.

[#413582] g++ must be called for c++ extensions
[#454030] distutils cannot link C++ code with GCC

topdir = "Lib/distutils"

* bcppcompiler.py
  (BCPPCompiler.create_static_lib): Fixed prototype, removing extra_preargs
  and extra_postargs parameters. Included target_lang parameter.
  (BCPPCompiler.link): Included target_lang parameter.

* msvccompiler.py
  (MSVCCompiler.create_static_lib): Fixed prototype, removing extra_preargs
  and extra_postargs parameters. Included target_lang parameter.
  (MSVCCompiler.link): Included target_lang parameter.

* ccompiler.py
  (CCompiler): New language_map and language_order attributes, used by
  CCompiler.detect_language().

  (CCompiler.detect_language): New method, will return the language of
  a given source, or list of sources. Individual source language is
  detected using the language_map dict. When mixed sources are used,
  language_order will stablish the language precedence.

  (CCompiler.create_static_lib, CCompiler.link, CCompiler.link_executable,
   CCompiler.link_shared_object, CCompiler.link_shared_lib):
  Inlcuded target_lang parameter.

* cygwinccompiler.py
  (CygwinCCompiler.link): Included target_lang parameter.

* emxccompiler.py
  (EMXCCompiler.link): Included target_lang parameter.

* mwerkscompiler.py
  (MWerksCompiler.link): Included target_lang parameter.

* extension.py
  (Extension.__init__): New 'language' parameter/attribute, initialized
  to None by default. If provided will overlap the automatic detection
  made by CCompiler.detect_language(), in build_ext command.

* sysconfig.py
  (customize_compiler): Check Makefile for CXX option, and also the
  environment variable CXX. Use the resulting value in the 'compiler_cxx'
  parameter of compiler.set_executables().

* unixccompiler.py
  (UnixCCompiler): Included 'compiler_cxx' in executables dict, defaulting
  to 'cc'.
  (UnixCCompiler.create_static_lib): Included target_lang parameter.
  (UnixCCompiler.link): Included target_lang parameter, and made
  linker command use compiler_cxx, if target_lang is 'c++'.

* command/build_ext.py
  (build_ext.build_extension): Pass new ext.language attribute
  to compiler.link_shared_object()'s target_lang parameter. If
  ext.language is not provided, detect language using
  compiler.detect_language(sources) instead.

* command/config.py
  (config._link): Pass already available lang parameter as target_lang
  parameter of compiler.link_executable().

This is a conservative version of SF patch 504889.  It uses the log
module instead of calling print in various places, and it ignores the
verbose argument passed to many functions and set as an attribute on
some objects.  Instead, it uses the verbosity set on the logger via
the command line.

The log module is now preferred over announce() and warn() methods
that exist only for backwards compatibility.

XXX This checkin changes a lot of modules that have no test suite and
aren't exercised by the Python build process.  It will need
substantial testing.

Tom Loredo.

- compile() didn't return a (empty) list of objects. Fixed.
- the various _fix_xxx_args() methods weren't called (are they new or did I overlook them?). Fixed.