Merge 8.6, which means some more Tk_GetPixelsFromObj() improvements #385

Job	Run time
test (gcc)	3m 45s
build (gcc)	1m 45s
test (gcc, --disable-xft)	3m 47s
build (gcc, CFLAGS=-DTK_NO_DEPRECATED=1)	1m 49s
test (gcc, --enable-symbols)	3m 18s
build (gcc, --disable-xft)	1m 57s
build (gcc, --disable-xss)	1m 38s
build (gcc, --enable-symbols)	1m 15s
build (clang)	2m 31s
build (clang, CFLAGS=-DTK_NO_DEPRECATED=1)	1m 48s
build (clang, --disable-xft)	1m 50s
build (clang, --disable-xss)	1m 48s
build (clang, --enable-symbols)	1m 27s
	28m 38s

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