gitweb: improve long line wrapping behavior

gitweb: improve long line wrapping behavior

Move the ' ' separating the line number from the text into the
line number anchor and make it white-space:pre so that when
long lines get wrapped the line number sticks to the front of
the line rather than being on its own line because the ' '
after the line number allows a wrap to the next line.

This was not a problem prior to the change from using 'pre'
to 'pre-wrap'.  However, rather than revert, we do this because
'pre-wrap' is more browser compatible than 'break-word', so we
want to keep the pre-wrap change.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>