fix IL jumps highlighting in Text Viewer

change white background for icons in PouInstanceVariablePanel to transparent

in wxPython 2.8 panel has white background and therefore white
background is appropriate, but in wxPython 3.0 panel has grey
background (on GNU/Linux and on Windows).
Transparent background looks good on both wxPython versions and on all platforms.

change white background for project tree element to transparent

because on GNU/Linux project tree has grey background, therefore
white background looks not good.

fix second error message in case of error appearing too early to have a wx frame

fix a side effect of 95ecb26fdc4e

remove old unused .cvsignore

fix issue with printing scheme (FBD, LD or SFC) with comment element on GNU/Linux

If you draw FBD scheme and place comment on it and then try to print
it, then no wires will be printed and comment box is empty (text is
missing). This happens only for wx.PrinterDC and not on wx.MemoryDC
that is used to draw print preview window in Beremiz IDE.
Looks like a bug in wxPython or wxWidgets.

There were found several workaround for this issue.
1) If some dc.DrawLines call is placed before dc.DrawPolygon, then the
problem is gone.

...
dc.DrawLines(polygon)
dc.DrawPolygon(polygon)
...

2) Reseting DC brush solves the problem as well (see this changeset).

detect iec2c options and ieclib path only once during the first build