Mangle C++ contructors and destructors correctly
add missing null check
Merge pull request #2181 from yebblies/ctormangle

[DDMD] Mangle C++ contructors and destructors correctly
Merge pull request #2189 from WalterBright/fix_null_expression

Fix null expression
fix Issue 10334 - ddoc should prefer simple syntax for template instantiations with one parameter