Haxe allows C++ reserved keywords as variable names

I couldn't figure out the cause of my application not compiling to Android target for a long time. I used a variable named `compl` (for "completed") in my code. It turns out it is a reserved word in C++.

Possible solutions for Haxe:
* throw compilation error directly in Haxe when targeting C++ based on reserved keywords list (a lot of work involved)
* use `#undef compl` and undef all newer keywords (also a lot of work involved)
* replace names of the variables on C++ target: `compl` -> `package_line_compl` - package name, line where it was first defined and its name

This is potentially problematic for many other C-specific keywords, but the issue is of low/informative-priority.