Import libepoxy 1.2

dist/libepoxy/README.md

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+Epoxy is a library for handling OpenGL function pointer management for
+you.
+
+It hides the complexity of ```dlopen()```, ```dlsym()```,
+```glXGetProcAddress()```, ```eglGetProcAddress()```, etc. from the
+app developer, with very little knowledge needed on their part.  They
+get to read GL specs and write code using undecorated function names
+like ```glCompileShader()```.
+
+Don't forget to check for your extensions or versions being present
+before you use them, just like before!  We'll tell you what you forgot
+to check for instead of just segfaulting, though.
+
+Features
+--------
+
+* Automatically initializes as new GL functions are used.
+* GL 4.4 core and compatibility context support.
+* GLES 1/2/3 context support.
+* Knows about function aliases so (e.g.) ```glBufferData()``` can be
+  used with ```GL_ARB_vertex_buffer_object``` implementations, along
+  with GL 1.5+ implementations.
+* EGL, GLX, and WGL support.
+* Can be mixed with non-epoxy GL usage.
+
+Building
+--------
+
+    ./autogen.sh
+    make
+    sudo make install
+
+Dependencies for debian:
+
+* automake
+* libegl1-mesa-dev
+* xutils-dev
+
+Dependencies for OS X (macports):
+
+* automake
+* autoconf
+* xorg-util-macros
+* pkgconfig
+* xorg-libX11
+
+Other dependencies for OS X:
+
+* [XQuartz](http://xquartz.macosforge.org/landing/)
+
+The test suite has additional dependencies depending on the platform.
+(X11, EGL, a running X Server).
+
+Switching your code to using epoxy
+----------------------------------
+
+It should be as easy as replacing:
+
+    #include <GL/gl.h>
+    #include <GL/glx.h>
+    #include <GL/glext.h>
+
+with:
+
+    #include <epoxy/gl.h>
+    #include <epoxy/glx.h>
+
+As long as epoxy's headers appear first, you should be ready to go.
+Additionally, some new helpers become available, so you don't have to
+write them:
+
+```int epoxy_gl_version()``` returns the GL version:
+
+* 12 for GL 1.2
+* 20 for GL 2.0
+* 44 for GL 4.4
+
+```bool epoxy_has_gl_extension()``` returns whether a GL extension is
+available (```GL_ARB_texture_buffer_object```, for example).
+
+Note that this is not terribly fast, so keep it out of your hot paths,
+ok?
+
+Why not use libGLEW?
+--------------------
+
+GLEW has several issues:
+
+* Doesn't know about aliases of functions (There are 5 providers of
+  glPointParameterfv, for example, and you don't want to have to
+  choose which one to call when they're all the same).
+* Doesn't support GL 3.2+ core contexts
+* Doesn't support GLES.
+* Doesn't support EGL.
+* Has a hard-to-maintain parser of extension specification text
+  instead of using the old .spec file or the new .xml.
+* Has significant startup time overhead when ```glewInit()```
+  autodetects the world.
+* User-visible multithreading support choice for win32.
+
+The motivation for this project came out of previous use of libGLEW in
+[piglit](http://piglit.freedesktop.org/).  Other GL dispatch code
+generation projects had similar failures.  Ideally, piglit wants to be
+able to build a single binary for a test that can run on whatever
+context or window system it chooses, not based on link time choices.
+
+We had to solve some of GLEW's problems for piglit and solving them
+meant replacing every single piece of GLEW, so we built
+piglit-dispatch from scratch.  And since we wanted to reuse it in
+other GL-related projects, this is the result.
+
+win32 issues
+------------
+
+The automatic per-context symbol resolution for win32 requires that
+epoxy knows when ```wglMakeCurrent()``` is called, because
+wglGetProcAddress() return values depend on the context's device and
+pixel format.  If ```wglMakeCurrent()``` is called from outside of
+epoxy (in a way that might change the device or pixel format), then
+epoxy needs to be notified of the change using the
+```epoxy_handle_external_wglMakeCurrent()``` function.
+
+The win32 wglMakeCurrent() variants are slower than they should be,
+because they should be caching the resolved dispatch tables instead of
+resetting an entire thread-local dispatch table every time.