a Lexer reads tokens from a stream.
Define sets of token that are to be recognized as special keywords (as opposed to identifiers).
Construct a Lexer on the given Buffer using the given token set.
Return the origin of the given pointer (filename and line number)
Construct a Lexer on the given Buffer using the given token set. The default token set is CXX with GCC extensions.
Return the origin of the given pointer (filename and line number)
try to fill the token cache to contain at least o tokens. Returns false if there are not enough tokens.