add assert_eq! macro

the assert_eq! macro compares its arguments and fails if they're not
equal. It's more informative than fail_unless!, because it explicitly
writes the given and expected arguments on failure.
change some uses of fail_unless to assert_eq
add utility function to parse using tts

also, updates test cases a bit.
change to parsing using tts
tidy
Starting to add SyntaxContexts
adding MTWT functions
make idents managed
push path changes across other modules
foo
working
debugging...
marks, renaming, resolve functions implemented and tested
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tidy
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