build: Add option to compile for coverage reports

Add --coverage option to configure to support
compiling for generation of C based coverage reports

PR-URL: https://github.com/nodejs/node/pull/9463


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>