M-RET sends the wrong escape codes to the terminal

[bcc32]

Pressing M-RET (to be fully explicit, I am holding down the left alt key and pressing Enter, on a US ANSI keyboard) sends the wrong escape codes to the terminal, causing the running program to misinterpret the keystroke as some

$ showkey -a

Press any keys - Ctrl-D will terminate this program

^[[109;7u        27 0033 0x1b
         91 0133 0x5b
         49 0061 0x31
         48 0060 0x30
         57 0071 0x39
         59 0073 0x3b
         55 0067 0x37
        117 0165 0x75
^D        4 0004 0x04

In a terminal emulator like gnome-terminal, or using the built-in M-x term, the results are as expected:

$ showkey -a

Press any keys - Ctrl-D will terminate this program

^[^M     27 0033 0x1b
         13 0015 0x0d
^D        4 0004 0x04