libselinux: use reentrant strtok_r(3) #541

Job	Run time
build (gcc, 3.11, 3.1)	1m 39s
build (gcc, 3.11, 3.1, test-flags-override)	1m 21s
build (gcc, 3.11, 3.1, test-debug)	1m 26s
build (gcc, 3.11, 3.1, linker-bfd)	1m 33s
build (gcc, 3.11, 3.1, linker-gold)	1m 33s
build (gcc, 3.10, 3.1)	1m 47s
build (gcc, 3.9, 3.1)	1m 47s
build (gcc, 3.8, 3.1)	1m 38s
build (gcc, 3.7, 3.1)	1m 57s
build (gcc, pypy3.7, 3.1)	1m 50s
build (gcc, 3.11, 3.0)	1m 43s
build (gcc, 3.11, 2.7)	2m 14s
build (gcc, 3.11, 2.6)	2m 43s
build (gcc, 3.11, 2.5)	1m 39s
build (clang, 3.11, 3.1)	1m 44s
build (clang, 3.11, 3.1, test-flags-override)	1m 32s
build (clang, 3.11, 3.1, test-debug)	1m 32s
build (clang, 3.10, 3.1)	1m 47s
build (clang, 3.9, 3.1)	1m 49s
build (clang, 3.8, 3.1)	1m 51s
build (clang, 3.7, 3.1)	1m 42s
build (clang, pypy3.7, 3.1)	2m 2s
build (clang, 3.11, 3.0)	1m 35s
build (clang, 3.11, 2.7)	1m 48s
build (clang, 3.11, 2.6)	1m 58s
build (clang, 3.11, 2.5)	1m 46s
build (gcc, 3.11, 3.1, sanitizers)	2m 2s
	47m 58s

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