Add symbol parser (token.cc)
Add keyword parser (token.cc)
Make Skipper skip adjacent line continuations

Skipper should remove adjacent multiple line continuations.
Add isBlankOrNewline function
Add whitespaceSkipper function
Require locale in isBlank and isTokenDelimiter

Environments passed to character predicate functions must have a valid
locale. The functions should always call Environment::locale so that a
test will fail when the environment does not provide a locale regardless
of whether HAVE_STD__ISBLANK is zero or non-zero.
Add PipelineParser class