added MTWT functions
comments, cleanup
mod.rs cleanup and renaming
cleanup, renaming
syntax test cases pass
adding parse_path part 1
jbcdone tracking (should never wind up in upstream)
temp, shouldn't go upstream
adding parse_path part 2
moved tests to ast_util, changed to use idents as names
simplify, based on invariant that items_allowed != foreign_items_allowed
jbcdone, not to go upstream
using invariant again
jbcdone no upstream
not for upstream
remove unnecessary function
reindent in parser
not for upstream
unneccessary since tjc's commit 78ec6fe30cf2b, fixing #2804
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