Add another test for symbol renaming
Also fix name conflicts amongst fields and parameters
Also rename symbols named "_"
symbol renaming: Handle anonymous structs/unions
Move nested #defines to toplevel
Also fix name conflicts in parameters of procptr subtypes
cpp: Fix out-of-date comment
c: Shorten error message for atomic expressions
Remove GUI
test runner: Improve output
tests: Update for 1c1c903b
Improve error reporting by tracking expansion level of tokens
ast: Add TK node vs tk matching helper function
ast: Add astTakeLoc() helper
util: Use len() > 0 instead of <> ""