root testsuite: further revisions while investigating the problem.
libsyntax: made a bunch of fields pub as part of my investigation of the bug.
root testsuite: when reinvoking make recursively, use `$(MAKE)` to inherit actual binary and flags.
libsyntax: Extended parser with support for embedded hygiene.  FIXME

current unconditional.  I need to conditionalize this to ensure it is
only utilized from within quote_expr macro and friends.
libsyntax: embed Ident using special encoding that preserves hygiene.
libsyntax: method for encoding Ident for re-reading into token tree.
libsyntax: pprust support for encoding Ident's as (uint,uint) pairs (for hygiene).
libsyntax: add support to `quote_expr!` and friends for round-trip hygienic preservation of Ident.