Enhance ScriptCompiler to also dump API as C Header file.

The C Header file is intended to be 'force included' in the IDE to get content assist / code completion when editing AngelScript file in the C/C++ editor. The output section of DumpAPI() method is reordered slightly to keep the parser happy. This work is inspired by the work done by Vladimir Andri (see https://groups.google.com/forum/#!topic/urho3d/8WOOGAdwlEU).