Add stubs header for Snappy on Windows.

Taken from Chromium.
Also, remove all config.h - they are not used.
Turn off IPv6 by default.

Since it doesn't work right now.
Don't run tasks with already closed connections.
Fix PKG generation on Mac.
Refactor almost all code, using wrapped file handlers.

Except the network stuff. It will be later.
Fix some compilation issues on Windows.

And do some minor ports.
Fix compilation on Linux.

Don't know why, but libfile_cache requires libprotobuf with older clang
versions.
Fix compilation of c_utils.
Close pipes in |Process::Run()| before waiting for child to exit.

This may help to solve problem with a hanging Clang.
Fix compilation on Mac.

Mac OS X doesn't have the |pipe2| system call.
Push and pop macros for the log levels' names.

MSVC defines some of them right in system headers. Cool.
Major refactoring of networking part.

Use objects instead of raw file descriptors.
Fix compilation on Mac.
Fix compilation on Mac.
More macro for windows to compile