Add ctrl+r to the mac key map

data/keyboard-layouts/macos.keytab

@@ -16,6 +16,7 @@ key C+Ctrl : "\x03"     # interrupt
 key D+Ctrl : "\x04"     # logout "exit"
 key E+Ctrl : "\x05"     # goto end of line
 key L+Ctrl : "\x0C"     # clear terminal screen
+key R+Ctrl : "\x12"     # invoke shell history
 key U+Ctrl : "\x15"     # clear current line
 key V+Ctrl : "\x16"     #
 key W+Ctrl : "\x17"     # erase the word preceding to the cursor position