Merge nano proto into protobuf repository.

Update LICENSE to list files that aren't copyrighted by Google Inc.

Source: https://android.googlesource.com/platform/external/protobuf.git

Ignore files generated from new 'map*.protobuf' sources.

Fix compiler error: "a class-key must be used when declaring a friend"

google/protobuf/map_test.cc:88:16: error: expected ‘;’ at end of member declaration
google/protobuf/map_test.cc:88:18: error: ‘override’ does not name a type
.

Make .gitignore more robust

Don't rely on non-standard 'INT32_MAX' / 'INT32_MIN'.

Ignore generated test scaffolding files.

Exclude Python build artifacts.

Incorporates feedback from @xfxyjwf:
https://github.com/google/protobuf/pull/84#discussion_r20474781.

Define safe constants to use when padding enums.

Fixes #80.

This is following what V8 does:
https://code.google.com/p/v8/source/browse/trunk/LICENSE

Add AIX/POWER atomicops and fix compilation with IBM xlC C++ compiler.

- `int64` typedef collision with `sys/inttypes.h`
- `xlC` complains about `int` and pointer comparisons without casts

NDK libraries should not be linked in to platform code, so create a
separate version for the platform that is linked against libc++
instead of the NDK STLs.

Bug: 15193147
Change-Id: I3935e5dd3bd99676772a4b9681e275ef3601b855

Conflicts:
	src/google/protobuf/compiler/java/java_file.cc

setup.py fixes for Python 3

* commit 'dbb9c3033097e571e15c16d6e2e814be7e9d60bc':
  Added an API method in FieldData to allow access to the UnknownField data

Silence -Wsign-compare warning on Mac

Change-Id: I2cd5cfc80dce2a297fcd2511074b2a9d23d39837

Fixed Unused Parameter warning in headers.

Change references to `vector` to use `std::vector`