Bug#1009710: minor memory leaks

[Morel Bérenger]

The previous report was done after noticing a lot more of problems when
using the stack glfw3 + glm + epoxy + mesa with intel drivers.
Valgrind reports lot of memory problems notably when using
glCompileShader, when loading shared libraries (dlopen) and many more.
I can provide the source code that I'm writing which triggers those,
it's intended to be FOSS in any case, but it's very young and does
nothing interesting (taking my time to write code with every possible
error checking in the graphical stack).

I have not reported those information is original bug report, because
they do not belong directly to glfw3. Sending multiple reports would be
an option, but I'm not sure it's very productive, especially if this is
going to be ignored (problems are only seen with valgrind AFAIK and
some of those might be related to stuff I did in my code, notably the
shaders. I need to dig more to be confident enough there to send a
report.)