Default to OPTIMIZE=-g for developers with .git dir
Major update to SizeMe.xs

Added assertions to ensure:
    links only connect to nodes not links.
    Links only connect to nodes.
    SetNode is only called on node or placeholder.
Fixed some issues found by the assertions.
Added way to test is a pointer has been sized without flagging it as sized.
Renamed some links and nodes.
Fixed refcounted_he_data size for threaded perl
Reordered steps in perl_size.
Grouped sizing free space into separate node
Don't sv_size PL_main_root and PL_main_start as they're OPs I think