[ES] Fixed loading of OpenGL ES core API

eglGetProcAddress cannot be used to retrieve
entry points of core functions. Instead, we
use [DllImport] for core functions and function
pointers for extension functions.

Squashed commit of the following:

commit 0b84aa6ef78dfa3600b81fc412eb192f2a87e40c
Author: thefiddler <stapostol@gmail.com>
Date:   Sat Mar 15 02:24:58 2014 +0100

    [Examples] Rolled back changes to Example browser

commit 1acfbaac3d17184debdbbe872c58ac07d1b37c0a
Author: thefiddler <stapostol@gmail.com>
Date:   Sat Mar 15 02:20:57 2014 +0100

    [Examples] Rolled back WinForms example

commit 835d9d6035a890bd3426566929fbfd25c493eca0
Author: thefiddler <stapostol@gmail.com>
Date:   Sat Mar 15 01:15:01 2014 +0100

    [Examples] Rolled back erroneous GLControl mods

commit 056418014f0e835e83fb85b54b8749519a555364
Author: thefiddler <stapostol@gmail.com>
Date:   Fri Mar 14 23:11:11 2014 +0100

    [Rewrite] Remove calli prototypes

    When a function is called indirectly via a function pointer, its
    prototype is not required (the prototype is added as a callsite at the
    calli invocation.) Removing these prototypes reduces binary size by
    roughly 400KB.

commit 353a16ec2836c597150d2fab28581e7c264b2b39
Author: thefiddler <stapostol@gmail.com>
Date:   Fri Mar 14 22:31:25 2014 +0100

    [Rewrite] Call DllImports directly

    When a function does not have an allocated slot (i.e. slot = -1), then
    we will call its DllImport signature directly.

commit 9a5313e4b7afb10b698d255e4b5637887bf71cf3
Author: thefiddler <stapostol@gmail.com>
Date:   Fri Mar 14 22:30:04 2014 +0100

    [Bind] Do not allocate slots for DllImports

commit 6ac5342409363cac0e59f9dc669948b319bd20a9
Author: thefiddler <stapostol@gmail.com>
Date:   Fri Mar 14 22:29:07 2014 +0100

    [Bind] Added option to use DllImports

    This is necessary for the core functionality of OpenGL ES, where
    eglGetProcAddress returns null or garbage (the latter on Android.)
[SDL2] On Mac, OpenGL 3.0 or 3.1 should create 3.2 context

SDL2/Mac fails to create a 3.0 or 3.1 OpenGL context. We implicitly
bump version to 3.2, otherwise 3.0 or 3.1 would give a 2.1 context.