Remove std::iterator from Boost Regex search code:
std::iterator was deprecated in C++17.
Remove it to fix the warnings and avoid other issues.
Fix#10035, close#10036
The performance issue, which appears after switching to static linkage of libSciLexer, is due to th commit "Improve character case handling in RegEx" (#9707).
Removing "locale" call from "BoostRegexSearch::FindText()" solves auto-completion performance issue.
Fix#9975, close#10010
Don Ho