Fix rcamera.h issues

[ghost]

This PR address part of "REVIEW: Example: core_3d_camera_free. Displayed controls do not match and camera behaves strangely." from #2952.

1. Fixes CAMERA_FREE behaving strangely (unintended rolling while yawing and pitching) by setting rotateUp to false (R439). This change does not impact the other cameras, because rotateUp is already false for them.

2. Fixes CAMERA_FREE mouse wheel zoom by adding it to the zoom mode check (R503).

3. Adds pan to CAMERA_FREE by adding handling for it before mouse and keyboard handling (R462-R472) and a define for CAMERA_PAN_SPEED (R187).

4. Readds up (Space) and down (Left Ctrl) movement to CAMERA_FREE (R496-R500). This change does not impact the other cameras because it was already disabled for them.

Tested these proposed changes successfully on PLATFORM_DESKTOP on Linux (Linux Mint 21.1 x86_64) and PLATFORM_WEB.

Edit: added line marks.

[raysan5]

@ubkp Nice! Thank you very much for the improvement! :)

[ghost]

@raysan5 Still on this topic, the core_3d_camera_free displayed control mentions "Alt + Mouse Wheel Pressed to Rotate" (L74), but I don't understand this one. Isn't that the same as just moving the mouse? Do you remember what it meant by that?

[raysan5]

@ubkp Mouse wheel was possible to be pressed as an additional button, actually the control scheme was the same one used by 3d max and other 3d softwares to navigate the scene.

In any case, camera does not necessarily follow those controls, new ones could be added and the text changed for consistency.

[ghost]

@raysan5 Got it. Thank you very much for the explanation.