A few more message tweaks and a correction for r9482.

* subversion/svnadmin/main.c
* subversion/svnlook/main.c
  Capitalize an error message.
* subversion/clients/cmdline/main.c
  Reintroduce a space in a help message removed by mistake in r9482.

Index: subversion/svnadmin/main.c
===================================================================
--- subversion/svnadmin/main.c	(revision 9496)
+++ subversion/svnadmin/main.c	(working copy)
@@ -1003,7 +1003,7 @@
           subcommand = svn_opt_get_canonical_subcommand (cmd_table, first_arg);
           if (subcommand == NULL)
             {
-              fprintf (stderr, _("unknown command: '%s'\n"), first_arg);
+              fprintf (stderr, _("Unknown command: '%s'\n"), first_arg);
               subcommand_help (NULL, NULL, pool);
               svn_pool_destroy (pool);
               return EXIT_FAILURE;
Index: subversion/svnlook/main.c
===================================================================
--- subversion/svnlook/main.c	(revision 9496)
+++ subversion/svnlook/main.c	(working copy)
@@ -1917,7 +1917,7 @@
           subcommand = svn_opt_get_canonical_subcommand (cmd_table, first_arg);
           if (subcommand == NULL)
             {
-              fprintf (stderr, _("unknown command: '%s'\n"), first_arg);
+              fprintf (stderr, _("Unknown command: '%s'\n"), first_arg);
               subcommand_help (NULL, NULL, pool);
               svn_pool_destroy (pool);
               return EXIT_FAILURE;
Index: subversion/clients/cmdline/main.c
===================================================================
--- subversion/clients/cmdline/main.c	(revision 9496)
+++ subversion/clients/cmdline/main.c	(working copy)
@@ -206,7 +206,7 @@
      svn_cl__editor_cmd_opt, svn_cl__encoding_opt, svn_cl__config_dir_opt} },
   
   { "copy", svn_cl__copy, {"cp"},
-    N_("Duplicate something in working copy or repository, remembering"
+    N_("Duplicate something in working copy or repository, remembering "
        "history.\n"
        "usage: copy SRC DST\n"
        "\n"