WIP: PipelineParser: triple command with negation
Make Skipper skip adjacent line continuations

Skipper should remove adjacent multiple line continuations.
WIP: PipelineParser: line continuation and tab after !
WIP: PipelineParser: line continuation and tab after |
Add isBlankOrNewline function
Add whitespaceSkipper function
WIP: PipelineParser: newline after |
WIP: PipelineParser: delimiter after single command
WIP: PipelineParser: delimiter after double command
WIP: PipelineParser: need more source
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.
WIP: PipelineParser: use CLocaleEnvironmentStub