This should fix the GL loading errors that occur in some drivers due to
the use of deprecated functions by GLEW. Side benefits are more accurate
auto-completion (deprecated function and symbols don't exist) and faster
pointer loading (less entrypoints to load). In addition it removes an
external library depency, simplifying the build system a bit and
eliminating one set of binary libraries for Windows.
The Git for Windows installer doesn't add the Git binaries to the path
by default. (Due to risk of conflicts with built-in windows commands.)
Unless you have configured your system specially this causes the
scm_rev_gen.js script to fail to find Git. Added more paths to the
script so that it searches in the default msysgit installation
directory, eliminating the need to set the PATH for most environments.