BButton style fixes
BMenu: style fixes
BMenu: remove useless default case
BMenu: Replace min_c and max_c

... with std:min and std:max
BMenuBar style fixes
BMenuField: style fixes
BMenuField: Replace 5 with DefaultLabelSpacing()
BMenuField: Check if menuBar is NULL explicitly
BTextControl: style fixes
BMenuField/BTextControl: Store and reuse Label()