winedbg: Prevent syntax errors for list command due to the lexer.

winedbg: Prevent syntax errors for list command due to the lexer.

The list command allows more than just a pathname, but since a pathname
allows such a wide range of characters, it will prevent other parameters
from getting parsed properly (e.g. a start line number). This even
interfered with the usage of pathname for the list command, since the
command typically includes a line number within the file.