Remove useless #includes from Base.h and move to appropriate files.
Correctly handle split-reads of auxv data.
Use AnyProcessId instead of AllProcessId when none is specified.
Implement attach for debug session.

This commit keeps in place the now-empty SlaveSessionImpl. If it ends up
being purely useless, I'll get rid of it later when I restart working on
platform support.
Ignore packet checksums when we are in noAckMode.

noAckMode implies that checksums should not be checked. Implementations
may simply send "#00" as their checksum.
Separate the run and wait operations in ProcessSpawner.
Move platform-specific support files to their respective directories.
Stop using `assert' in favor of DS2ASSERT.

This makes sure that we get failed assertions in our log files and
uniformizes the output format.
Minor style fixups.

Just ran clang-format on every file.
Get rid of some dead code in ProcessSpawner.