git-review.1 manpage fix for groff warnings

The current manual page contains hyphens where a minus sign
was intended. By default, "-" chars are interpreted as
hyphens (U+2010) by groff, not as minus signs (U+002D).
Since options to programs use minus signs (U+002D), this
means for example in UTF-8 locales that you cannot cut and
paste options, nor search for them easily.

This patch fixes this by escaping hyphens with backslashes.

Change-Id: I66e8041366ced24dac2ac21bbcf49de67a63c75b
Merge "git-review.1 manpage fix for groff warnings"