Merge pull request #65 from farcaller/plugin_registrar

Updated macros to new rust plugin framework

Reviewed-by: bharrisau
Bump gcc version for travis.
Refactored platformtree code into a crate.
Simpler syntax for testing; also moved some tests around.
Removed platformtree/test. Never used it.
node::Path now tracks its Span.
Store subnodes in GCs vector (was boxes vector).
Added some test implementation for lpc17xx clock PT.
Added slightly better testing framework.
Extracted lpc PT code to hal/lpc17xx/platformtree.rs.
Extracted lpc PT tests.
Added some comments on what’s going on.
Renamed TokenSource to ClockSource.
Slightly better generated code thanks to inline 'use'.
Code cleanup.