Removed whitespace and added dtools/bin/remove-whitespace as a tool to do this in the future.

The sed script was provided by Moritz Fischer.

Implements ticket:401 and ticket:402.

Adds several API functions to determine build constants at runtime, and
a convenience command line program to display them:

From C++:

const std::string gr_prefix();
const std::string gr_sysconfdir();
const std::string gr_prefsdir();...