More work on options window

dropdown function
Prefer the RCT2_GLOBAL macro
Increase the warning_throttle array size to hold all 7 values
Merge branch 'duncanspumpkin-master'
Merge branch 'master' of https://github.com/adrian17/OpenRCT2 into adrian17-master
Merge branch 'adrian17-master'
options window mouseup code
Merge branch 'options-window' of https://github.com/ddevrien/OpenRCT2 into ddevrien-options-window
fix warnings in options window
Merge branch 'ddevrien-options-window'
Merge branch 'options-window' of https://github.com/ddevrien/OpenRCT2 into ddevrien-options-window
Merge branch 'ddevrien-options-window'