Export point accessors point-line and point-linum.

[mychris]

Small change which exports the two accessors point-line and point-linum.
There might be more functions which should be exported but I didn't go through the whole file.

[Sasanidas]

LGTM!

[cxxxr]

The line structure is an internal structure and should not be exported.
The point-linum is also an internal structure and should be exported using the function line-number-at-point instead.

[cxxxr]

Nevertheless, I appreciate your attempts to improve it.

[mychris]

Thanks for pointing me to the correct API. I couldn't find it, and since the API to get the point from the buffer is public, and all the other functions regarding point are public, I guessed those should be as well.