using unix sockets for AISC broken

[epruesse]

Since r4672 unix sockets cannot be used anymore for e.g. arb_pt_server:

arb_pt_server -Dmydb.arb -T:/tmp/arb_pt_$USER_$$

Suggested fix: Only prefix 'localhost' to socket string if it not just begins with a ':', but also continues with a number.

Index: SERVERCNTRL/servercntrl.c
===================================================================
--- SERVERCNTRL/servercntrl.c   (revision 5469)
+++ SERVERCNTRL/servercntrl.c   (working copy)
@@ -326,7 +326,8 @@
                 case 'P': erg->pt_server     = strdup(argv[s]+2);break;
                 case 'T': {
                     char *ipport = argv[s]+2;
-                    if (ipport[0] == ':') { /* port only -> assume localhost */
+                    if (ipport[0] == ':' &&
+                        ipport[1] >= '0' && ipport[1] <= '9') { /* port only -> assume localhost */
                         erg->tcp = GBS_global_string_copy("localhost%s", ipport);
                     }
                     else {