fix Issue 13538 - Divide old C style syntax from D style grammar rule
fix Issue 13539 - Disallow optional template parameters with C-style syntax
Divide DeclaratorIdentifier to VarDeclaratorIdentifier and newly added AltDeclaratorIdentifier
Merge pull request #664 from 9rnsr/fix_declaration

Issue 13538 & 13539 - Improve variable declaration grammar for old C style syntax