Draft approach towards resolving https://github.com/micropython/micropython/issues/560#issuecomment-42213955
Merge branch 'keep-strings-uninterned' of github.com:pfalcon/micropython into pfalcon-keep-strings-uninterned

Conflicts:
	py/parse.c
py: Don't automatically intern strings in parser.

This completes non-automatic interning of strings in the parser, so that
doc strings don't take up RAM.  It complicates the parser and compiler,
and bloats stmhal by about 300 bytes.  It's complicated because now
there are 2 kinds of parse-nodes that can be strings: interned leaves
and non-interned structs.
Merge branch 'pfalcon-keep-strings-uninterned'