Add a DEBUG option to scons, use it for debugging info and stricter compiler warnings. For issue #96: add the -Wmissing-prototypes flag to cc in DEBUG mode.
Add a DEBUG option to scons, use it for debugging info and stricter
compiler warnings.
For issue #96: add the -Wmissing-prototypes flag to cc in DEBUG mode.

* SConstruct: Add DEBUG argument. Move option reading before setting the build
     parameters. Set -g and -Wmissing-prototypes only in DEBUG mode, -O2 only
     in !DEBUG mode.

jandre/serf,jandre/serf,jandre/serf,jandre/serf