Update protobuf version (protocolbuffers#6472)

Update protobuf version (protocolbuffers#6366)

Merge pull request protocolbuffers#6298 from TeBoring/3.9.x-merge

Merge master into 3.9.x

Merge pull request protocolbuffers#6160 from haon4/3.8.x-20190521140707

Update protobuf version to 3.8.0

Merge pull request protocolbuffers#6083 from haon4/changes3_8_0

Update change log for 3.8.0

Update version number to 3.7.1 (protocolbuffers#5947)

* Update version number to 3.7.1

* Update version number in port_def.inc

Update version number to 3.7.0 (protocolbuffers#5793)

* Update version number to 3.7.0

* Add php/releash.sh to Makefile.am

* Make cpp_distcheck exit on fail

Merge pull request protocolbuffers#5766 from TeBoring/3.7.x-fix

Update version number to 3.7.0rc3

Protocol Buffers v3.7.0rc2

Fixed infinite recursion problem with Java GeneratedMessageV3 (protoc…

…olbuffers#5657)

GeneratedMessageV3#setUnknownFieldsProto3 was trying to delegate to
setUnknownFields but was inadvertently resulting in infinite recursion.
This commit makes setUnknownFields and setUnknownFieldsProto3 delegate
to a common private method to fix the problem and avoid confusion.