patch 8.2.3406: on some systems tests fail without _REENTRANT

Problem:    On some systems tests fail without _REENTRANT. (Elimar
            Riesebieter)
Solution:   Add -D_REENTRANT in configure. (closes #7402)

src/auto/configure

@@ -14960,6 +14960,10 @@ $as_echo "no" >&6; }
   fi
 fi
 
+if `echo "$CFLAGS" | grep -v D_XEENTRANT >/dev/null`; then
+  CFLAGS="$CFLAGS -D_REENTRANT"
+fi
+
 DEPEND_CFLAGS_FILTER=
 if test "$GCC" = yes; then
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for GCC 3 or later" >&5

src/configure.ac

@@ -4504,6 +4504,12 @@ if test "$MACOS_X" = "yes"; then
   fi
 fi
 
+dnl On some systems REENTRANT needs to be defined.  It should not hurt to use
+dnl it everywhere.
+if `echo "$CFLAGS" | grep -v D_REENTRANT >/dev/null`; then
+  CFLAGS="$CFLAGS -D_REENTRANT"
+fi
+
 dnl gcc 3.1 changed the meaning of -MM.  The only solution appears to be to
 dnl use "-isystem" instead of "-I" for all non-Vim include dirs.
 dnl But only when making dependencies, cproto and lint don't take "-isystem".

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3406,
 /**/
     3405,
 /**/