Fix [29ba539501] for listbox: many PIXEL options don't keep their con… #454

Job	Run time
build (gcc)	1m 59s
test (gcc)	3m 57s
build (gcc, CFLAGS=-DTK_NO_DEPRECATED=1)	1m 40s
test (gcc, --disable-xft)	4m 3s
build (gcc, --disable-xft)	2m 0s
test (gcc, --enable-symbols)	3m 42s
build (gcc, --disable-xss)	1m 40s
build (gcc, --enable-symbols)	1m 16s
build (clang)	1m 56s
build (clang, CFLAGS=-DTK_NO_DEPRECATED=1)	1m 47s
build (clang, --disable-xft)	2m 11s
build (clang, --disable-xss)	1m 53s
build (clang, --enable-symbols)	1m 28s
	29m 32s

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