Ignore .gcov_report files

Signed-off-by: Casey Dahlin <casey.dahlin@gmail.com>
Replace GCOV with LCOV

Well that was a short trip. We're using LCOV now for coverage due to shiny HTML
reporting. Also some of the libtool hammering has been removed on account of
either libtool or gcov has figured out how to negotiate with the other without
need of anything special.

Signed-off-by: Casey Dahlin <casey.dahlin@gmail.com>