Big patch from Rene Liebscher to simplify the CCompiler API and
* replace 'link_shared_object()', 'link_shared_lib()', and
'link_executable()' with 'link()', which is (roughly)
the union of the three methods it replaces
* in all implementation classes (UnixCCompiler, MSVCCompiler, etc.),
ditch the old 'link_*()' methods and replace them with 'link()'
* in the abstract base class (CCompiler), add the old 'link_*()'
methods as wrappers around the new 'link()' (they also print
a warning of the deprecated interface)
Also increases consistency between MSVCCompiler and BCPPCompiler,
hopefully to make it easier to factor out the mythical WindowsCCompiler
* use 'self.linker' instead of 'self.link'
* add ability to compile resource files to BCPPCompiler
* added (redundant?) 'object_filename()' method to BCPPCompiler
* only generate a .def file if 'export_symbols' defined