Log Message:
Update to 3.51

Upstream changes:
3.51 - 2019-05-01

    * include the module version in metadata for proper PAUSE indexing

 3.50 - 2019-04-30

    * Order warn before uv for packWARN (shown in 5.6.1)

 3.49 - 2019-04-29

    * Fix tests for 64bit int, 32bit ptr platforms

 3.48 - 2019-04-28

    * Order misc before uv for UNLIKELY (<=5.8.8)

 3.47 - 2019-04-27

    * re-fix leaky code (used only in tests)