Wrap columns to 80 characters.

- To do this I had to move the return types and function signatures
onto their own lines in many header files. We already do this in most
.c files. Due to this I've changed all the function declarations to
use this same style.
- Remove trailing whitespace.
Change var name in string.c

- Changed webvtt_string res to be called out as this is more clear
as to what it is actually for.
Make webvtt_string_append comments more clear
Merge pull request #379 from RickEyre/wrap-80-chars

Wrap columns to 80 characters.
Migrate to Waf build system
Removed 'webvtt-config-win32.h' which is no longer needed
Gitignore some generated files
More control over warnings
Valgrind build on travis
Unbreak MSVC build. fewer MSVC warnings
Test fix in scripts/tools/pthread.py