Fix setting COM_Parse current line number

Fix initial off-by-one error.
Count lines in /* */ comments and multi-line strings.
Fix counting some lines twice if text has Unix newlines.
Check for shaders without closing brace

Shaders without closing brace can eat shaders in other files.
Pass depth to SkipBracedSection instead of reparsing text as it messed up parse line numbers.
Improve warning for shader missing opening brace