Check for and use gettid() directly if available; glibc 2.30 and later
provides a wrapper for the system call:
* configure.in: Check for gettid() and define HAVE_SYS_GETTID if
gettid() is only usable via syscall().
* server/log.c (log_tid): Use gettid() directly if available.
Submitted by: jorton
Reviewed by: jorton, jfclere, gbechis
Github: closes#404
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1915544 13f79535-47bb-0310-9956-ffa450edef68