Document that _REENTRANT is not needed explicitly.

README

@@ -414,16 +414,20 @@ send in the patch.  (Don't bother patching the configure script itself
 Compiler switches for threads
 .............................
 
+The definition of _REENTRANT should be configured automatically, if
+that does not work on your system, or if _REENTRANT is defined
+incorrectly, please report that as a bug.
+
     OS/Compiler/threads                     Switches for use with threads
-    (POSIX is draft 10, DCE is draft 4)     (1) compile only (2) compile & link
+    (POSIX is draft 10, DCE is draft 4)     compile & link
 
-    SunOS 5.{1-5}/{gcc,SunPro cc}/solaris   (1) -D_REENTRANT   (2) -mt
-    SunOS 5.5/{gcc,SunPro cc}/POSIX         (1) -D_REENTRANT
-    DEC OSF/1 3.x/cc/DCE                    (1) -D_REENTRANT   (2) -threads 
+    SunOS 5.{1-5}/{gcc,SunPro cc}/solaris   -mt
+    SunOS 5.5/{gcc,SunPro cc}/POSIX         (nothing)
+    DEC OSF/1 3.x/cc/DCE                    -threads 
 	    (butenhof@zko.dec.com)
-    Digital UNIX 4.x/cc/DCE                 (1) -D_REENTRANT   (2) -threads 
+    Digital UNIX 4.x/cc/DCE                 -threads 
 	    (butenhof@zko.dec.com)
-    Digital UNIX 4.x/cc/POSIX               (1) -D_REENTRANT   (2) -pthread 
+    Digital UNIX 4.x/cc/POSIX               -pthread 
 	    (butenhof@zko.dec.com)
     AIX 4.1.4/cc_r/d7                       (nothing)                       
 	    (buhrt@iquest.net)