threadlib: optimize on Solaris 10 or newer

[Bruno Haible]

It was reported in <https://savannah.gnu.org/bugs/?32087>
that the PTHREAD_IN_USE_DETECTION_HARD setting that causes
a dummy thread to be created at runtime, just to see whether
multithreading is really enabled, is no longer necessary in Solaris 10.

This is true according to the Solaris doc:
https://docs.oracle.com/cd/E19205-01/819-5264/afanb/index.html
https://docs.oracle.com/cd/E18752_01/html/816-5137/compile-94611.html


2016-12-10  Bruno Haible  <address@hidden>

        threadlib: Optimize out runtime test on Solaris >= 10.
        * m4/threadlib.m4 (gl_THREADLIB_BODY): Don't set
        PTHREAD_IN_USE_DETECTION_HARD if configuring on Solaris 10 or newer.
        Reported by Peter Felecan at <https://savannah.gnu.org/bugs/?32087>.

diff --git a/m4/threadlib.m4 b/m4/threadlib.m4
index b43534e..2b6b6cf 100644
--- a/m4/threadlib.m4
+++ b/m4/threadlib.m4
@@ -1,4 +1,4 @@
-# threadlib.m4 serial 11 (gettext-0.18.2)
+# threadlib.m4 serial 12
 dnl Copyright (C) 2005-2016 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -195,8 +195,10 @@ int main ()
              # Therefore pthread_in_use() needs to actually try to create a
              # thread: pthread_create from libc will fail, whereas
              # pthread_create will actually create a thread.
+             # On Solaris 10 or newer, this test is no longer needed, because
+             # libc contains the fully functional pthread functions.
              case "$host_os" in
-               solaris* | hpux*)
+               solaris | solaris2.[1-9] | solaris2.[1-9].* | hpux*)
                  AC_DEFINE([PTHREAD_IN_USE_DETECTION_HARD], [1],
                    [Define if the pthread_in_use() detection is hard.])
              esac