pg_regress now needs to know that Windows hasn't got unix sockets,

per Andrew Dunstan.  Also, don't override the user's value of PGHOST
in the 'make installcheck' case.  I think the latter was an ill-considered
workaround for the Windows code back when libpq didn't properly default
to localhost on Unix-socket-less platforms.

src/test/regress/pg_regress.sh

 #! /bin/sh
-# $PostgreSQL: pgsql/src/test/regress/pg_regress.sh,v 1.52 2005/01/12 16:19:51 tgl Exp $
+# $PostgreSQL: pgsql/src/test/regress/pg_regress.sh,v 1.53 2005/01/15 04:15:51 tgl Exp $
 
 me=`basename $0`
 : ${TMPDIR=/tmp}
@@ -192,11 +192,10 @@ esac
 
 
 # ----------
-# When on QNX or BeOS, don't use Unix sockets.
+# On some platforms we can't use Unix sockets.
 # ----------
-
 case $host_platform in
-    *-*-qnx* | *beos*)
+    *-*-cygwin* | *-*-mingw32* | *-*-qnx* | *beos*)
         unix_sockets=no;;
     *)
         unix_sockets=yes;;
@@ -470,13 +469,6 @@ else # not temp-install
             ;;
     esac
 
-    # If Unix sockets are not available, use the local host by default.
-    if [ "$unix_sockets" = no ]; then
-        PGHOST=$hostname
-        export PGHOST
-        unset PGHOSTADDR
-    fi
-
     if [ -n "$PGPORT" ]; then
         port_info="port $PGPORT"
     else
@@ -486,15 +478,13 @@ else # not temp-install
     if [ -n "$PGHOST" ]; then
         echo "(using postmaster on $PGHOST, $port_info)"
     else
-        case $host_platform in
-            *-*-mingw32*)
-                echo "(using postmaster on localhost socket, $port_info)"
-                ;;
-            *)
+        if [ "$unix_sockets" = no ]; then
+            echo "(using postmaster on localhost, $port_info)"
+        else
             echo "(using postmaster on Unix socket, $port_info)"
-                ;;
-        esac
         fi
+    fi
+
     message "dropping database \"$dbname\""
     "$bindir/dropdb" $psql_options "$dbname"
     # errors can be ignored