Design compile time api hs_compile_lit() and hs_compile_lit_multi()
to handle pure literal pattern sets. Corresponding option --literal-on
is added for hyperscan testing suites. Extended parameters and part of
flags are not supported for this api.
Successful analysis of a pattern with hs_expression_info() does not
imply that the pattern will successfully compile with hs_compile(), etc.
It is merely a utility function for pattern analysis.
Addresses Github issue #54.
