Modify TkTextGetTabs() signature: textPtr -> tkwin #396

Job	Run time
test (gcc)	3m 45s
build (gcc)	1m 35s
test (gcc, --disable-xft)	3m 51s
build (gcc, CFLAGS=-DTK_NO_DEPRECATED=1)	1m 37s
test (gcc, --enable-symbols)	3m 16s
build (gcc, --disable-shared)	1m 34s
build (gcc, --disable-xft)	1m 39s
build (gcc, --disable-xss)	1m 37s
build (gcc, --enable-symbols)	1m 12s
build (clang)	1m 45s
build (clang, CFLAGS=-DTK_NO_DEPRECATED=1)	1m 50s
build (clang, --disable-shared)	1m 47s
build (clang, --disable-xft)	1m 47s
build (clang, --disable-xss)	1m 50s
build (clang, --enable-symbols)	1m 31s
	30m 36s

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