Check for and use gettid() directly if available; glibc 2.30 and later #684

Job	Run time
Empty APLOGNO() test	39s
Default	3m 39s
All-static modules	3m 30s
Prefork MPM, all-modules (except cgid)	4m 12s
Worker MPM, all-modules	4m 4s
Shared MPMs, all-modules	4m 10s
Event MPM, all-modules, mod_cgid only	4m 15s
Event MPM, all-modules, no CMSG_DATA	4m 6s
Default, all-modules + install	4m 18s
Default, all-modules, random test order	3m 55s
GCC 10 maintainer-mode w/-Werror, install + VPATH	3m 10s
All-modules, APR 1.7.4, APR-util 1.6.3	5m 55s
APR 1.8.x, APR-util 1.7.x	5m 38s
Pool-debug	5m 55s
Shared MPMs (event), pool-debug, SSL/TLS variants	7m 46s
Shared MPMs (worker), pool-debug, SSL/TLS variants	8m 12s
Shared MPMs (prefork), pool-debug, SSL/TLS variants	8m 29s
litmus WebDAV tests	2m 17s
APR 1.7.4, APR-util 1.6.3, LDAP	5m 58s
APR trunk thread debugging	4m 31s
ASan	6m 39s
ASan, pool-debug	6m 48s
HTTP/2 test suite	13m 46s
MOD_TLS test suite	7m 20s
	2h 9m 12s

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