Remove support for leap-minutes (I thought I already removed that) #4651

Job	Run time
gcc	3m 23s
gcc (CFLAGS=-DTCL_NO_DEPRECATED=1)	3m 19s
gcc (--disable-shared)	3m 21s
gcc (--disable-zipfs)	3m 18s
gcc (--enable-symbols)	3m 36s
gcc (--enable-symbols=mem)	4m 55s
gcc (--enable-symbols=all)	6m 18s
gcc (CFLAGS=-ftrapv)	3m 31s
gcc (CFLAGS=-m32 CPPFLAGS=-m32 LDFLAGS=-m32 --disable-64bit)	3m 34s
	35m 15s

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