[Bugfix & Enchancement?] Clicking on the sound slider plays the sound at wrong volume
This pull request does two things: the first commit is a bug-fix, the second one is a related adjustment.
The sound slider in the game menu plays the move sound at the previous volume level when clicked on, as clicking itself will play the same sound (gmenu.cpp) and because of that the duplicate in gamemenu.cpp/gmenu_left_mouse will never play again. This fix makes the left click not play a sound when clicked on the sound slider as an exception. If there's a better way to do it, let me know!
The second one changes the minimum volume from -100.0 dB to -60.0 dB. Initially I thought the sound slider was wrong, as moving it to the middle almost made the music go silent, but after checking the code, it seems to be working perfectly, logarithmic conversion et al, just the minimum value seems to be way too low and this caused the slider to seem off. -60.0 dB is arbitrary, but in my opinion, -100.0 dB seems too low in any case.
Why remove range from the volume? I can still hear sound till 4 notches from the bottom.