Topography/XShape: Fix non-OpenGL polygon shape rendering

Fixes trac issue #3245.

The old code rendered polygons having holes using
  "points[0]        ...  points[lines[0]-1],
  "points[0]        ...  points[lines[1]-1], ..
instead of
  "points[0]        ...  points[lines[0]-1],
  "points[lines[0]] ...  points[lines[1]-1], ..

This caused issues for shapes containing holes, e.g. water
areas with islands.
Screen/Memory/RasterCanvas: Fix rendering of clipped polylines

Fixes trac issue #3250.

Given a closed polygon A-B-C-A where A-B requires clipping B to B'
giving a clipped line A-B' it is not valid to then draw the line
B'-C. Instead clipping needs to be performed again on B for the
line B-C giving B'' to render B''-C.
Manual en: Fix reference to devices sync settings
doc/manual: Fix truncated lines

Fixes trac issue #3247.
Topography/XShape: Don't show "UNK" shapes labels

Occurred on many water areas, probably short for "unknown".
Gauge/FlarmTrafficWindow: Always initialize pens, colors and brushes

Silence compiler "may be used uninitialized" warnings by
introduction of a (unused but safe fallback) default case in
switch statement.
Gauge/FlarmTrafficWindow: Always initialize circle_pen

Silence compiler "may be used uninitialized" warnings.
The initialization is not needed (circle_pen is only used if
"circles > 0") so this change causes a slight performance penalty
in the general case.
Gauges/LogoView: Always initialize titlex/titley

Silence compiler "may be used uninitialized" warnings.
MapWindow/GlueMapWindow: Always initialize min_time

Silence compiler "may be used uninitialized" warnings by
introduction of a (unused but safe fallback) default case in
switch statement.