Add -release switch to buildall.sh help, change coverage options.
Add -release switch to buildall.sh help, change coverage options.

This change documents the -release switch. It also removes the _debug
and _release suffixes from -codecoverage_* and determines them from
the presence of -release. On top of that it adds sanity checks to the
specified options.

Change-Id: Id69791264cb2d9e0ffe96a7ac5aabc34a553a7be
Reviewed-on: http://gerrit.cloudera.org:8080/2043
Reviewed-by: Alex Behm <fe1626037acfc2dc542d2aa723a6d14f2464a20c@cloudera.com>
Tested-by: Internal Jenkins

michaelhkw/incubator-impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,cloudera/Impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala