configure.in: fix lgamma_r condition

* configure.in (rb_cv_lgamma_r_m0): fix the condition for
  lgamma_r(-0.0).  [Bug #12249]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54503 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Wed Apr  6 22:41:31 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* configure.in (rb_cv_lgamma_r_m0): fix the condition for
+	  lgamma_r(-0.0).  [Bug #12249]
+
 Wed Apr  6 17:38:42 2016  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* tool/downloader.rb (RubyGems.download): follow the change of the

configure.in

@@ -2516,8 +2516,11 @@ int
 main(int argc, char **argv)
 {
     int sign;
+    double x = lgamma_r(-0.0, &sign);
 
-    if (lgamma_r(-0.0, &sign) >= 0) return EXIT_FAILURE;
+    /* should be [+inf, -1] */
+    if (x <= 0) return EXIT_FAILURE;
+    if (!isinf(x)) return EXIT_FAILURE;
     if (sign != -1) return EXIT_FAILURE;
     return EXIT_SUCCESS;
 }