Reduce size of some svg icons.

Reduce size of some svg icons.

The svg files produced by vector editors may end up containing a lot
of unused elements that increase their size without any impact on
quality. For example, this occurs when copy/pasting between images
such that unused effects or shadings simply clutter the files.
Removing these elements in some cases may reduce the size to one half
or one third of the original one, leaving unmodified the image quality.