Documentation/technical: avoid stray backslash in parse-options API docs

Documentation/technical: avoid stray backslash in parse-options API docs

Due to some unpleasant interaction between the `quote', 'italics',
and `monospace` rules, a certain paragraph ends up rendered like so:

	‘short` is a character for the short option
	  (e.g. <tt>'e\’</tt> for <tt>-e</tt>, use <tt>0</tt> to omit),

Use the {apostrophe} to avoid this.

While at it, escape "->" strings: they are meant as a literal
two-character C operator, not a right-pointing arrow.

Reported-by: Frédéric Brière <fbriere@fbriere.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>