MFC of r358061:

Use 0x5c for the scan code 0x7d.

Japanese keyboards traditionally use 0x5c for
both Japanese yen sign key and backslash key.
While a Japanese yen sign is depicted on the keytop,
most of Japanese expect that the scan code 0x7d gives
a backslash (0x5c), not a Japanese yen sign (0xa5).

This is because JIS X 0201 encoding (aka ISO/IEC 646-JA,
an extended version of ASCII which is very popular
in Japan) has Japanese yen sign at 0x5c and
no backslash. On the other hand, ISO/IEC 8859-1
has Japanese yen sign at 0xa5. This difference has
caused a confusion after Unicode became popular since
ISO/IEC 10646 adopted 8859-1 for the plane 0.