Inconsistencies related to buffer texture pnames

In the latest refpages on the `glGet` page, `GL_TEXTURE_BINDING_BUFFER` has two incompatible definitions :
```
GL_TEXTURE_BINDING_BUFFER

data returns a single value, the name of the texture currently bound to the target GL_TEXTURE_BUFFER. The initial value is 0. See glBindTexture.
```
```
GL_TEXTURE_BINDING_BUFFER

data returns a single value, the name of the buffer object currently bound to the GL_TEXTURE_BUFFER buffer binding point. The initial value is 0. See glBindBuffer.
```
Moreover, `glGetTexLevelParameter` does not list `GL_TEXTURE_BUFFER_DATA_STORE_BINDING` as an accepted pname, in contrast with eg the OpenGL ES 3 refpages that do list it. Besides, the OpenGL 4.6 core spec makes no mention of this pname.

Worthy of note is also that the refpage for `glBindBuffer` does not mention a pname for getting the buffer bound to `GL_TEXTURE_BUFFER`.

Start with the glGet, glGetTexLevelParameter, and glBindBuffer reference pages mentioned in the issue, then compare their pname descriptions with the OpenGL 4.6 core specification and OpenGL ES 3 reference pages. Done means the buffer-texture binding and data-store pnames are consistently documented wherever applicable, with no conflicting definitions.

Written by the indexing model from the issue text.