Windows IME: Fix duplicated initial character when entering numbers
while in Chinese full width character mode.

While entering text with MS PinYin IME, you can optional select to enter full width versus half-width versions of a small number of characters. The fullwidth and halfwidth forms Unicode block are mostly for entering some narrow characters with a width compatible with regular Chinese characters. It is also used to enter some narrow versions of some normally-wide characters.

When in regular mode (halfwidth), pressing the numbers 0-9 will enter those regular characters, so these are NOT altered by the IME. But they are converted when in full width mode. We don't test for this mode, which means in our current code entering "0" when in fullwidth mode will result in "0０", both a regular zero and wide zero.

This patch just checks for fullwidth mode and adds 0-9 as characters processed by the IME.