* optimization: MainWindow resize event (no more issue #148)

minimap: Brightness-aware shading on side gaps

* CarlaStyle: more careful rounded corner drawing

Rounded rectangles have transparent corners even with opaque colors.
During compositing colors from several such objects are mixed,
producing unexpected artifacts. Also outer contour must have
bigger rounding - values for inner/outer rects are spreaded to be
around of original 2.0px, to preserve original look.

* CarlaStyle: better separator color

Create separator color from softened text color.

* paramspinbox: Keep scrollbar size closer to outer frame

Unless QStyle allowes any widget style, or it is entries and scrollbars
provide essential way to control or read frame parameters, scrollbar is
still set a bit smaller to counter theme-side deviations between
scrollbar and spinbox visible height while real height is equal.

* CarlaStyle: better light shade

* CarlaStyle: fix visible spinbox height regression

When spinbox is in one row with scrollbar or entry field, all vertically
expanding, spinbox look a bit lower.

* CarlaStyle: completed spinbox buttons light border

* CarlaStyle: fixed spinbox button rects, better borderwidth balance

Integer button rectangles now produce pixel-aligned non-overlaping,
still centered rectangles. SpinBox border width is reduced to minimum,
right enough to keep entry widget corners out of outer rounded border
parts.

* CarlaStyle: constification (SpinBox drawing)

* CarlaStyle: spinbox drawing fixes

Rely to correct buttons rectangles, handle correctly both even and odd
spinbox heights. Disappeared buttons highlight glitch, appeared when
moving mouse one button to another.

* CarlaStyle, SpinBox: contrast highlight margin between buttons

* CarlaStyle spinbox: more careful buttons highlight

* CarlaStyle, spinbox: better arrows placement

* paramspinbox: Hide scrollbar border

* CarlaStyle: nicer rounded corners in deep-dark colors (less radius deviation)

* CarlaStyle CT_ToolButton: took less space than combobox in same layout

As in designer, carla_host.ui has plus/minus buttons size 25x24, with
height equal to adjacent combobox. It seems, system carla style already
got fix.