VIM-771 Fix semicolon repeat for 'till char' motion

Fixes https://youtrack.jetbrains.com/issue/VIM-771

Based on empirical testing with Vim, ';' should work like this:
assuming "<caret>1:a 2:b 3:c" with ':' as the last f/t character:

- "t:" does nothing
- ";"  cursor goes to '2'
- "2;" cursor goes to '2', same as the previous
- "3;" cursor goes to '3'