Merge branch 'cmake-configure-fixes-v2'

Merge branch 'cmake-configure-fixes-v2'

Fixes in cmake, to make it more like configure and support some
cross-compiling.

* cmake-configure-fixes-v2:
  cmake: fix extracting of the version from git (check for number of matches)
  Detect arch4random_addrandom() existence
  Use off_t instead of ev_off_t for sendfile() (fixes android build)
  cmake: detect _GNU_SOURCE not by __GNU_LIBRARY__ only (fallback to _GNU_SOURCE)
  Check for WNOWAIT in waitpid() in runtime (not in cmake/configure)
  cmake: add <pthread.h> into CMAKE_REQUIRED_INCLUDES for sizeof(pthread_t)
  cmake: fix values for #cmakedefine
  cmake: drop duplicates from event-config template
  cmake: add value for the #cmakedefine macros (like autoconf)
  cmake: Fix checking of enum values from sysctl.h

(cherry picked from commit 5aade2d30b6c5eff226cbf7b63fda5a01987ba4f)