add new Literal API for pure literal expressions:

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.

src/fdr/fdr_confirm.h

@@ -62,7 +62,6 @@ struct LitInfo {
     u8 size;
     u8 flags; //!< bitfield of flags from FDR_LIT_FLAG_* above.
     u8 next;
-    u8 pure; //!< The pass-on of pure flag from hwlmLiteral.
 };
 
 #define FDRC_FLAG_NO_CONFIRM 1