do not use unsetenv.c on mingw

configure

@@ -17448,8 +17448,121 @@ LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
 
 
 
+for ac_func in crypt getopt getrusage inet_aton random rint srandom strdup strerror strlcat strlcpy strtol strtoul
+do
+as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
+{ echo "$as_me:$LINENO: checking for $ac_func" >&5
+echo $ECHO_N "checking for $ac_func... $ECHO_C" >&6; }
+if { as_var=$as_ac_var; eval "test \"\${$as_var+set}\" = set"; }; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+/* Define $ac_func to an innocuous variant, in case <limits.h> declares $ac_func.
+   For example, HP-UX 11i <limits.h> declares gettimeofday.  */
+#define $ac_func innocuous_$ac_func
+
+/* System header to define __stub macros and hopefully few prototypes,
+    which can conflict with char $ac_func (); below.
+    Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
+    <limits.h> exists even on freestanding compilers.  */
 
-for ac_func in crypt getopt getrusage inet_aton random rint srandom strdup strerror strlcat strlcpy strtol strtoul unsetenv
+#ifdef __STDC__
+# include <limits.h>
+#else
+# include <assert.h>
+#endif
+
+#undef $ac_func
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char $ac_func ();
+/* The GNU C library defines this for functions which it implements
+    to always fail with ENOSYS.  Some functions are actually named
+    something starting with __ and the normal name is an alias.  */
+#if defined __stub_$ac_func || defined __stub___$ac_func
+choke me
+#endif
+
+int
+main ()
+{
+return $ac_func ();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_link") 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } && {
+	 test -z "$ac_c_werror_flag" ||
+	 test ! -s conftest.err
+       } && test -s conftest$ac_exeext &&
+       $as_test_x conftest$ac_exeext; then
+  eval "$as_ac_var=yes"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+	eval "$as_ac_var=no"
+fi
+
+rm -f core conftest.err conftest.$ac_objext conftest_ipa8_conftest.oo \
+      conftest$ac_exeext conftest.$ac_ext
+fi
+ac_res=`eval echo '${'$as_ac_var'}'`
+	       { echo "$as_me:$LINENO: result: $ac_res" >&5
+echo "${ECHO_T}$ac_res" >&6; }
+if test `eval echo '${'$as_ac_var'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_func" | $as_tr_cpp` 1
+_ACEOF
+
+else
+  case " $LIBOBJS " in
+  *" $ac_func.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS $ac_func.$ac_objext"
+ ;;
+esac
+
+fi
+done
+
+
+
+case $host_os in
+
+        # Windows uses a specialised env handler
+        mingw*)
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_UNSETENV 1
+_ACEOF
+
+                ac_cv_func_unsetenv=yes;;
+        *)
+
+for ac_func in unsetenv
 do
 as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
 { echo "$as_me:$LINENO: checking for $ac_func" >&5
@@ -17550,6 +17663,9 @@ fi
 done
 
 
+		;;
+esac
+
 
 LIBS="$pgac_save_LIBS"
 

configure.in

 dnl Process this file with autoconf to produce a configure script.
-dnl $PostgreSQL: pgsql/configure.in,v 1.590 2009/02/11 20:02:39 tgl Exp $
+dnl $PostgreSQL: pgsql/configure.in,v 1.591 2009/02/12 15:12:47 adunstan Exp $
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -1242,7 +1242,19 @@ fi
 pgac_save_LIBS="$LIBS"
 LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
 
-AC_REPLACE_FUNCS([crypt getopt getrusage inet_aton random rint srandom strdup strerror strlcat strlcpy strtol strtoul unsetenv])
+AC_REPLACE_FUNCS([crypt getopt getrusage inet_aton random rint srandom strdup strerror strlcat strlcpy strtol strtoul])
+
+case $host_os in
+
+        # Windows uses a specialised env handler
+        mingw*)
+                AC_DEFINE(HAVE_UNSETENV, 1, [Define to 1 because replacement version used.])
+                ac_cv_func_unsetenv=yes;;
+        *)
+                AC_REPLACE_FUNCS([unsetenv])
+		;;
+esac
+
 
 LIBS="$pgac_save_LIBS"