[Ohrrpgce] SVN: teeemcee/8693 tileedit: store preview_content flag in TileEditState to preserve it whe

[subversion at HamsterRepublic.com]

teeemcee
2017-04-27 20:40:46 -0700 (Thu, 27 Apr 2017)
237
tileedit: store preview_content flag in TileEditState to preserve it when changing tiles

However, unlike the sprite editor, nothing is preserved when leaving the
tile picker and going back to the maptile editor, except the clone buffer.
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U   wip/custom_udts.bi
U   wip/drawing.bas