All: Recompress PNG images

### File size reductions
Total change -4532
<table>
<tr><td>-689</td><td>themes/base/images/ui-icons_454545_256x240.png</td></tr>
<tr><td>-689</td><td>themes/base/images/ui-icons_888888_256x240.png</td></tr>
<tr><td>-689</td><td>themes/base/images/ui-icons_cd0a0a_256x240.png</td></tr>
<tr><td>-688</td><td>themes/base/images/ui-icons_222222_256x240.png</td></tr>
<tr><td>-688</td><td>themes/base/images/ui-icons_2e83ff_256x240.png</td></tr>
<tr><td>-306</td><td>demos/selectmenu/images/24-podcast-square.png</td></tr>
<tr><td>-224</td><td>demos/selectmenu/images/24-rss-square.png</td></tr>
<tr><td>-200</td><td>demos/selectmenu/images/24-video-square.png</td></tr>
<tr><td>-94</td><td>themes/base/images/ui-bg_flat_0_aaaaaa_40x100.png</td></tr>
<tr><td>-94</td><td>themes/base/images/ui-bg_flat_75_ffffff_40x100.png</td></tr>
<tr><td>-68</td><td>demos/autocomplete/images/jquery_32x32.png</td></tr>
<tr><td>-16</td><td>themes/base/images/ui-bg_glass_75_dadada_1x400.png</td></tr>
<tr><td>-15</td><td>themes/base/images/ui-bg_glass_65_ffffff_1x400.png</td></tr>
<tr><td>-14</td><td>demos/autocomplete/images/transparent_1x1.png</td></tr>
<tr><td>-14</td><td>themes/base/images/ui-bg_glass_75_e6e6e6_1x400.png</td></tr>
<tr><td>-12</td><td>tests/unit/images/jqueryui_32x32.png</td></tr>
<tr><td>-9</td><td>themes/base/images/ui-bg_glass_55_fbf9ee_1x400.png</td></tr>
<tr><td>-8</td><td>demos/autocomplete/images/jqueryui_32x32.png</td></tr>
<tr><td>-7</td><td>themes/base/images/ui-bg_highlight-soft_75_cccccc_1x100.png</td></tr>
<tr><td>-6</td><td>themes/base/images/ui-bg_glass_95_fef1ec_1x400.png</td></tr>
<tr><td>-2</td><td>demos/autocomplete/images/sizzlejs_32x32.png</td></tr>
</table>