m4: Update ax_func_posix_memalign to the latest version. #771

Job	Run time
linux rpm fedora	10m 22s
osx clang --disable-ssl	5m 43s
dpdk gcc	9s
linux gcc --disable-ssl	3m 21s
linux clang --disable-ssl	3m 28s
linux gcc test -500	21m 14s
linux gcc test 501-1000	11m 45s
linux gcc test 1001-	7m 29s
linux clang test sanitizers -300	16m 24s
linux clang test sanitizers 301-600	23m 57s
linux clang test sanitizers 601-900	12m 36s
linux clang test sanitizers 901-1200	10m 22s
linux clang test sanitizers 1201-	9m 50s
linux gcc test -ljemalloc -500	22m 37s
linux gcc test -ljemalloc 501-1000	13m 2s
linux gcc test -ljemalloc 1001-	8m 34s
linux gcc system-test-dpdk dpdk -100	16m 15s
linux gcc system-test-dpdk dpdk 101-200	23m 7s
linux gcc system-test-dpdk dpdk 201-	24m 53s
linux gcc system-test-userspace -100	14m 59s
linux gcc system-test-userspace 101-200	19m 24s
linux gcc system-test-userspace 201-	22m 47s
linux gcc system-test -100	15m 26s
linux gcc system-test 101-200	20m 28s
linux gcc system-test 201-	24m 5s
linux clang system-test sanitizers -100	17m 17s
linux clang system-test sanitizers 101-200	22m 37s
linux clang system-test sanitizers 201-	26m 30s
linux x86 gcc --disable-ssl	2m 40s
	7h 11m 21s

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