Fix double minus signs in manual pages

Fix double minus signs in manual pages

This patch fixes the following lintian(1) warning: "Manual page seems
to contain a hyphen where a minus sign was intended. '-' 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&paste options, nor search
for them easily. '-' must be escaped ('\-') to be interpreted as minus."