Don't overwrite existing files with ;s.

Closes issue #914.

common/locale/en-US/messages.properties

@@ -207,6 +207,8 @@ io.eNotDir = Not a directory
 io.eNotDir-1 = Not a directory %S
 io.exists = File exists (add ! to override)
 io.exists-1 = File %S exists (add ! to override)
+# XXX
+io.existsNoOverride-1 = File %S exists
 io.noCommand-1 = Command not found: %S
 io.noPrevDir = E186: No previous directory
 io.noSuchDir-1 = E344: Can't find directory %S