OSL release v1.11.13.0

Larry Gritz

We have tagged v1.11.13.0 (a.k.a. Release- as the latest supported production release of OSL, and the "release" branch marker has been updated to this spot. This is guaranteed to be API, ABI, and link compatible with prior 1.11.x releases. Release notes are below.

Also, we recently tagged "dev-" as a "developer snapshot" for those who wish to use the master branch at a known stable point. (But note: as a pre-release development branch, we DO NOT make any promises whatsoever that ABI or even API compatibility will not change before 1.12 is an official release branch later this year.)

Release 1.11.13 -- 1 Apr 2021 (compared to 1.11.12)
* Updated vector2.h with a `mod(vector2,vector2)` function. #1312
* Fix unnecesary error messages to stderr when encountering broken point
clouds. #1333

Larry Gritz