* plug-ins/common/cartoon.c
	* plug-ins/common/cubism.c
	* plug-ins/common/displace.c
	* plug-ins/common/dog.c
	* plug-ins/common/emboss.c
	* plug-ins/common/engrave.c
	* plug-ins/common/gauss.c
	* plug-ins/common/glasstile.c
	* plug-ins/common/neon.c
	* plug-ins/common/noisify.c
	* plug-ins/common/oilify.c
	* plug-ins/common/photocopy.c
	* plug-ins/common/ripple.c
	* plug-ins/common/sharpen.c
	* plug-ins/common/shift.c
	* plug-ins/common/sobel.c
	* plug-ins/common/softglow.c
	* plug-ins/common/spread.c
	* plug-ins/common/tileit.c
	* plug-ins/common/whirlpinch.c: make sure tile cache is allocated
	before preview is shown -- significant speedup in some cases,
	minimal in others.

	* plug-ins/common/sel_gauss.c: give it a tile cache (didn't
	have one).  Still very slow but a little better.