... and add a few basic statistics about the number of requests, ASTs
built, etc. The Statistic type is loosely based on the one from LLVM,
but suitable for using without DEBUG macros and using SourceKit UIdents
to identify the statistic. The easiest way to add a new statistic is to
add it to SwiftStatistics.def in the SwiftLangSupport.
Added "-help" option to Options.td
Added also:
* Added "OPT_HELP" case in the main TestOptions.cpp switch. It uses the llvm options help functionality to provide up-to-date help
* Additional "Use -help for assistance" at the end of the error message that appears when calling an unknown option
Added their following tests, respectively::
* usage.swift, and
* wrong_arguments.swift
Extra: FIXME: in TestOptions::printHelp, suggesting a possible expansion for the printHelp option (details in file)
