Add --gcov-options '\-lp' to coverage

Should result in more accurate header file coverage, see
https://github.com/eddyxu/cpp-coveralls/issues/54Reviewed-by: NKurt Roeckx <kurt@openssl.org>

.travis.yml

@@ -114,7 +114,7 @@ script:
 
 after_success:
     - if [ -n "$COVERALLS" ]; then
-          coveralls -b .;
+          coveralls -b . --gcov-options '\-lp';
       fi;
 
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