[Ohrrpgce] SVN: teeemcee/8400 Add new backdrop browser, supporting larger backdrops stored in .rgfx fo

[subversion at HamsterRepublic.com]

teeemcee
2017-02-17 04:31:33 -0800 (Fri, 17 Feb 2017)
399
Add new backdrop browser, supporting larger backdrops stored in .rgfx format

It is unfinished, since it doesn't actually save backdrops, nor does
Ctrl+Backdrop work, but it's otherwise functional. So for now it is hidden.

This menu is a copy of importbmp without too many changes. After
it is finished, importbmp will only be for tilesets. And longer term,
tilesets will also be converted to rgfx.
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U   wip/allmodex.bas
U   wip/custom.bas
U   wip/custom.bi
U   wip/drawing.bas
U   wip/loading.bi
U   wip/loading.rbas
U   wip/util.bi