Merge third_party/usrsctp/usrsctplib from https://chromium.googlesource.com/external/usrsctplib.git at e6e18333da18c5bb7de7e9189e53403e2ffa7023

This commit was generated by merge_from_chromium.py.

Change-Id: I8a11747334b96417bbacde937399eb1fc271ef6c