extractdecls.lua: in command-line parsing, remove hard-codedness of 'x'.
Minor documentation tweaks.
Factor out command line parsing into parsecmdline_pk.lua.

Also, really remove hard-codedness of 'x'.
Allow creating TranslationUnit_t object that map to the same CXTranslationUnit.

Also, add cur:translationUnit() and cur:isDefinition().
Add prototypical searcher for named member accesses, mgrep.lua.

Useful for working with codebases that have various struct types (currently:
must be typedef'd) with same-named members.
Add some documentation.
mgrep: extract lines reading directly from the source files.

The libclang API doesn't seem to have a way of getting raw text -- containing
exactly the same whitespace as the source.