Rename "backend" headers

Working on Vulkan clarified what has always been slightly smelly about the
design and organization here: not everything that is API specific is really in
a "backend" (a PuglBackend).  The concrete example is puglGetProcAddress(),
which only makes sense for GL and is actually implemented in the "backend"
files.  Arguably puglGetContext() is also such a thing.

So, rename the headers so they can be the place where API-specific things go in
general, which happens to include a backend most of the time.  The stub is a
bit of an exception to this, but whatever.  The includes look tidier this way.

In place of the old headers are compatibility stubs that just emit a warning
and include the new version, which will be maintained for a while.

1 files changed, 2 insertions, 2 deletions

diff --git a/pugl/pugl.h b/pugl/pugl.h
index fa75878..d4f079e 100644
--- a/pugl/pugl.h
+++ b/pugl/pugl.h
@@ -719,8 +719,8 @@ typedef struct PuglBackendImpl PuglBackend;
 
    This needs to be called once before creating the window to set the graphics
    backend.  There are two backend accessors included with pugl:
-   puglGlBackend() and puglCairoBackend(), declared in pugl_gl_backend.h and
-   pugl_cairo_backend.h, respectively.
+   puglGlBackend() and puglCairoBackend(), declared in pugl_gl.h and
+   pugl_cairo.h, respectively.
 */
 PUGL_API PuglStatus
 puglSetBackend(PuglView* view, const PuglBackend* backend);