Don't reuse the attribute-generating path in rule_parser's out-param … …overload of call. Doing so was wiping out previous partial results, in cases like foo >> bar, where foo produces a T, and bar is a rule that produces vector<T>. Fixes boostorg#248.

Remove space from declaration of UDLs, because apparently it matters?! Fixes boostorg#216.

Add doc example of unexpected combining sequence parsers. Example is based on boostorg#215.

Fix stale comment in doc example. 

Doc update for previous symbol table changes. Related to boostorg#183.