Removed some related functions

Followed from PR #3333.

(bongo/dancemat/adapter…)

Now we require lots of empty functions, but this removes by far more duplicated code.

Using the XPM format for images has become a maintenance problem because
people don't know how to create them. This commit removes all XPM images
and all C files that contain PNG images. DolphinWX now uses the PNGs
in the Resources folder instead, just like DolphinQt and DolphinQt2 do.

StrToWxStr is needed, otherwise the string will not be read as UTF-8.

Commit 33487ab5f20309e33b4734dbea9201b5b0d893a2 introduced a regression
where items would vanish from the toolbar. This adds a call to Realize()
after the reinsertions of the play/pause button as required per
documentation.

Thanks to Simonwayneee for noticing this!

Mark more strings for translation

This fixes changing the play/pause button's label depending on the
emulation state. Before, wxToolBarToolBase's SetLabel() function was
used. This function, however, is not implemented in wxGTK which leads to
the label not changing on linux when the button is clicked. Although the preferred
method (according to the wxWidgets documentation) to change the properties
of a tool is to use the toolbar's setters, there is no such setter for
the label. Therefore, this implements a workaround where the
button is deleted and readded afterwards with the updated properties.

Thanks to linkmauve for noticing this!

DolphinWX: Add a filename column