Changes to the build system.

* Integrated changes from cairo-samples build system into muHTTPd.
* Added support (rules) for build from C source files.
* Fixed bug causing constant bin and obj directory creation.
* Added new make script to set build system tools.
* Switch C++ compiler from GCC to GPP.
* Added new wxWidgets make script to set wx flags.
* Modified muHTTPdemo and libmuHTTPd make files.