Ordinal numbers weren't necessary. It's a legacy function from Win16.
Also refactor the def file generator to be much simpler.

Will be helpful for adding the libGLESv2 EGL entry points to the DEF
files. This will enable loading the right GLES libs on Linux and Mac
once we break the link dependency of libEGL on libGLESv2.

Bug: angleproject:2871
Bug: angleproject:2621
Change-Id: Ia2585323b076446af55359d875a6b67bcdc4d6f9
Reviewed-on: https://chromium-review.googlesource.com/c/1372378
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>