path -> Path
removed eval.rs: dead code

@brson confirms that eval.rs is now dead code
unneccessary since tjc's commit 78ec6fe30cf2b, fixing #2804
removed test referring to WONTFIX bug #2443
libsyntax comments only
move interner_key macro
added MTWT functions
reformulation in progress
comments, cleanup
parser comments only
refactor parse_fn_decl
syntax test cases now pass
adding parse_path
jbcdone tracking (should never wind up in upstream)
simplify, based on invariant that items_allowed != foreign_items_allowed
remove unnecessary function
reindent in parser
get rid of prec.rs

prec.rs no longer had much to do with precedence; the token->binop
function fits better in token.rs, and the one-liner defining the
precedence of 'as' can go next to the other precedence stuff in
ast_util.rs
comments
top-of-file comment for syntax.rc