Plasma::LineEdit uses the button text color for its text. Do the same
in PlasmaComponents.TextField to avoid white text on white background with
Oxygen theme.
Also use button text color for PC.TextArea because it uses the same
background frame as PC.TextField (P.TextEdit, its C++ equivalent, does not
have any background frame)
REVIEW: 105159
It seems that there's not a single theme out there which properly sets
viewTextColor. The background of textedits is white, so the text has to
be black. On Air(-mobile) this is not a problem, since the text is black
anyway, on dark themes (which set the text color to white), text simply
isn't visible.
We'll have to look into how themes implement viewtextcolor, should
probably fix the themes instead of the components, but this makes it
work until we do.
