Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  Fix an exception slicing issue in binpac generated cleanup code.
Updating submodule(s).

 [nomail]
Updating submodule(s).

 [nomail]
Adding an interface to manually control the buffering for generated
parsers.

This consists of two parts:

    1. The generated Flow classes expose their flow buffers via a new
       method flow_buffer().

    2. Flow buffers get two new methods:

        // Interface for delayed parsing. Sometimes BinPAC doesn't get the
        // buffering right and then one can use these to feed parts
        // individually and assemble them internally. After calling
        // FinishBuffer(), one can send the uppper-layer flow an FlowEOF()
        // to trigger parsing.
        void BufferData(const_byteptr data, const_byteptr end);
        void FinishBuffer();
Updating submodule(s).

 [nomail]
Updating submodule(s).

 [nomail]
Switching to relative submodule paths
Add BinPAC documentation from the old Bro wiki

Added the document "BinPAC Userguide" from the old Bro wiki to the existing
BinPAC README.
Remove some answers from the Q&A section of README
Merge branch 'topic/dnthayer/oldwiki-binpac'

BIT-1066 #merged
Fix double-free.

The field is deleted by a base class dtor.
Fix two use-after-free bugs.
Add missing va_end()'s to match va_start()'s.

Probably not an issue on most implementations, but undefined behavior
is scary and it's easy to fix.
Remove unreachable code.
Add missing break to switch statement case.