Fix error reporting for parallel parsed function blocks.

Fixes error reporting in function blocks by adding a start address
with parallel parses, and then using the getErrorBitNo() method
of the bitstream cursor to correct error bit number, based on the
start address.

Dependent on CL https://codereview.chromium.org/1851163002.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4363
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1848313003 .