Make the location of the Kerberos server key file run time configurable

(rather than compile time). For libpq, even when Kerberos support is
compiled in, the default user name should still fall back to geteuid()
if it can't be determined via the Kerberos system.

A couple of fixes for string type configuration parameters, now that there
is one.

configure.in

@@ -477,6 +477,8 @@ if test "$with_krb4" = yes ; then
   fi
   dnl Test for these libraries is below
   KRB_LIBS="$krb_libdir -lkrb -ldes"
+
+  krb_srvtab='/etc/srvtab'
 fi
 
 
@@ -513,6 +515,8 @@ if test "$with_krb5" = yes ; then
 
   dnl Test for these libraries is below
   KRB_LIBS="$krb_libdir -lkrb5 -lcrypto -lcom_err"
+
+  krb_srvtab='FILE:$(sysconfdir)/krb5.keytab'
 fi
 
 
@@ -521,6 +525,8 @@ if test "$with_krb4" = yes && test "$with_krb5" = yes ; then
   AC_MSG_ERROR([Kerberos 4 and Kerberos 5 support cannot be combined])
 fi
 
+
+AC_SUBST(krb_srvtab)
 dnl Necessary for special libpq link
 AC_SUBST(KRB_LIBS)
 
@@ -537,20 +543,6 @@ fi],
 [krb_srvnam="postgres"])
 AC_DEFINE_UNQUOTED(PG_KRB_SRVNAM, ["$krb_srvnam"], [The name of the Postgres service principal])
 
-AC_ARG_WITH(krb-srvtab, [  --with-krb-srvtab=FILE  location of Kerberos server's keytab file],
-[if test x"$withval" = x"yes"; then
-  AC_MSG_ERROR([argument required for --with-krb-srvtab])
-else
-  krb_srvtab=$withval
-fi],
-[if test "$with_krb5" = yes ; then
-  krb_srvtab='FILE:${sysconfdir}/krb5.keytab'
-elif test "$with_krb4" = yes ; then
-  krb_srvtab='/etc/srvtab'
-else
-  krb_srvtab=
-fi])
-AC_SUBST(krb_srvtab)
 
 
 #