RFR: Verification log is truncated

[Aleksey Shipilev]

When Matrix is enabled, the verification error log can be truncated, because
vmError code expects the _detailed_ message to be less than 1024 characters. The
workaround seems to be to call report_vm_error directly, which poses no limit to
the message length.

Webrev:
  http://cr.openjdk.java.net/~shade/shenandoah/verifier-no-trunc/webrev.01/

Thanks,
-Aleksey