2.7.1 is propably not considered stable yet. What i read quickly about TFPGMap too, is that there is no documentation yet because they're not even sure if they'll keep the syntax like that. It is the SVN version of freepascal, which i actually use along with SVN of Lazarus. Getting them compiled and running might be a little tricky though, but propably worth the effort.

If you want to compile fpc from source code, you need to do that with previous earlier stable release of FPC. For FPC 2.7.1 you propably need to download FPC 2.6.0 (or 2.6.1?) and compile SVN with that. There can be a bit fiddling with fpc.cfg configs, system PATH-variables and so on. I don't like to do that often... It's easier to update SVN Lazarus, assuming those fpc.cfg and PATH's are set right to point the SVN version FPC.