Fix text artifacts in example browser

[justincredible]

Fixes #4493

Thanks to @DaveH355 it was easy to git-bisect where the issue was introduced (31b9be8).

The diff is very short so it was quick to see the misuse of the VAO in glBindBuffer(). The first commit is sufficient for GLX, but testing on Windows showed a need to allocate the buffer space like the position VBO (I guess WGL is more faithful to the spec. in this regard?).

I also renamed the misleading variable to its supposed intended use.