* Make php message class final

Because proto messages are just data object, they should not be mocked.
Explicitly make them final to avoid accidental usage.

* Update generated descriptors

Removed all use of STLDelete*() in ObjC and C# Generators.

* php: Fixed php notices for unknown enum indices

* php: Fixed formatting of Duration

This fixes:
* Missing nanoseconds. The nanoseconds where divided as a float and
  implicitly converted to a string before being passed to bcadd.
  This can result in a float formatted in scientific/exponential notation,
  which bcmath doesn't understand.
* Durations are supposed to be formatted without trailing zeroes.

Other languages will have this removed inside Google first.
These functions are subject to ADL and cause problems.

Update GSON version to 3.8.5

Fixes #4079

value_field_typeclass should be a enum module, not EnumDescriptor
object.

Also expanding tests for enum valued maps.

Fixes #4580
Signed-off-by: Sorah Fukumori <her@sorah.jp>

Remove unused fields

Down Integrate to GitHub

Enabling silent mode by default to reduce make compilation noise

[Ruby] Remove to_hash methods

Make the JSON util string output functions match the Message::SerializeToString() behavior.  This is helpful when packing the output into string fields of reused protobuf messages.

As a followup to ca3ead77, treat plugin executables as well as protoc as host tools.

Follow up on https://github.com/protocolbuffers/protobuf/pull/6221

This avoids hitting the following warning when including GPBDescriptor.h in ARC
projects with stricter warning settings:
error: 'assign' property of object type may become a dangling reference; consider using 'unsafe_unretained' [-Werror,-Wobjc-property-assign-on-object-type

We first hit this in XCode 11, it's unclear whether it simply got stricter about
enforcing this warning or whether the flags enabled with -Wall or -Weverything
have been expanded.

In some platforms ${CMAKE_INSTALL_LIBDIR} expands to `lib64`. The libraries
are correctly installed in that directory, but the RPATH is set to point to
`$ORIGIN/../lib`, where it should be `$ORIGIN/../lib64`.

Merge 3.8.x into master branch

The wire_format_lite_inl.h header file was made unnecessary in #5839
and deleted in #5921, so remove the comment about it.

Update CONTRIBUTING.md to clarify who should set the labels

Down integrate to GitHub

release notes: no

I'm getting `src/google/protobuf/map_field.cc(284): error C2899: typename cannot be used outside a template declaration`

removing `typename` fixes the issue

This fixes compatibility with bazel when passing `--incompatible_no_support_tools_in_action_inputs` which will be flipped in an upcoming release.