Add implementations of open(2), mkdir(2), stat(2),
etc. that support long paths under Windows (paths
longer than MAX_PATH in <windows.h>, which is 260
characters).

The implementations are in a separate namespace
(google::protobuf::internal::win32), so they won't
collide with the standard implementations in
<io.h>, but after importing them with `using` they
can be drop-in replacements.

Fixes https://github.com/bazelbuild/bazel/issues/2634
Fixes https://github.com/google/protobuf/issues/2891

install 'generated_message_table_driven.h' and 'metadata_lite.h', they are included when compiling the files generated using protoc.exe 3.3.0

This allows the file path to contain spaces which is very common on
windows.

the deprecated atomics.

This is necessary so that the CMake build knows to include this header
file in the installation include/ directory.

This is necessary so that the CMake build knows to include this header
file in the installation include/ directory.

This pull request includes two implementation: C extension and PHP
package. Both implementations support encode/decode of singular,
repeated and map fields.

* `csharp_options`: Added `Options` to encapsulate generator options.
   Supported options for now - file_extension, base_namespace
* `{Blah}Generator`: Now accept `Options*` as parameter to constructor
* `csharp_generator.cc`: Parse and populate options
* `Makefile.am`: Added `csharp_options.h`
* `extract_includes.bat.in`: Added `csharp_options.h`

Refactoring code to two commits. This is the first commit

Change-Id: I6fa9f1b65d6c06b891aabf3f3d868364d74d727d

Change-Id: Ieb7a2c2fbf35bc2a8fa65b915a5ecb68c83863e4

Change-Id: I75459b8b6562c3ac58fa4b1e4513accdda43ad64

Change-Id: Ifbc415755266ba3d0ffa5661fcd7c7d2e3b32a22

Change-Id: I5049da7449cbada781aa1e23485a336b584802cb

Change-Id: Idecb2e3a5169f7b40d832242c9c10b0eb4325654

[ci skip]

Change-Id: I9391c09640e0b0b2b21c45a97a1fc91814d95c5d

Make it executable and generate extract_includes.bat in the same directory.