Fix to output a JSON buffer to an Unix domain socket.

Create the JSON buffer and write to it like regular file.

Upper function SCConfLogOpenGeneric already handle it properly.

Closes issue #1246.
Update Changelog for 2.1beta2 release
App-layer: Add Modbus protocol parser

Decode Modbus request and response messages, and extracts
MODBUS Application Protocol header and the code function.

In case of read/write function, extracts message contents
(read/write address, quantity, count, data to write).

Links request and response messages in a transaction according to
Transaction Identifier (transaction management based on DNS source code).

MODBUS Messaging on TCP/IP Implementation Guide V1.0b
(http://www.modbus.org/docs/Modbus_Messaging_Implementation_Guide_V1_0b.pdf)
MODBUS Application Protocol Specification V1.1b3
(http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf)

Based on DNS source code.

Signed-off-by: David DIALLO <diallo@et.esia.fr>
Detect: Add Modbus keyword management

Add the modbus.function and subfunction) keywords for public function match in rules (Modbus layer).
Matching based on code function, and if necessary, sub-function code
or based on category (assigned, unassigned, public, user or reserved)
and negation is permitted.

Add the modbus.access keyword for read/write Modbus function match in rules (Modbus layer).
Matching based on access type (read or write),
and/or function type (discretes, coils, input or holding)
and, if necessary, read or write address access,
and, if necessary, value to write.
For address and value matching, "<", ">" and "<>" is permitted.

Based on TLS source code and file size source code (address and value matching).

Signed-off-by: David DIALLO <diallo@et.esia.fr>
Detect-engine: Add Modbus detection engine

Management of Modbus Tx

Based on DNS source code.

Signed-off-by: David DIALLO <diallo@et.esia.fr>
Correct size increase in SigGroupHeadStore()

The code was increasing the size of the allocated memory by 16, but
only increasing the stored size by 10. Now uses one variable for both
places.
Coding style cleanup in detect-modbus files.
Remove an unused define COUNTER_DETECT_ALERTS

The only place this exists in the code is when it is defined.
Don't write target.tvar.idx in DetectFlowintParse

Match functions should not be writing to the SigMatch context. So just use
a local variable instead.
Fix bug in DetectFlowintParse() - Assigning to both parts of a Union

sfd->target.value was always being set, even if the targettype was
not FLOWINT_TARGET_VAL. This would cause the tvar to be overwritten
with garbage data.
DetectFlowintData - remove unused idx in TargetVar.

The idx inside TargetVar inside DetectFlowintData is never used, so remove
it.
Update copyright year in detect-flowbits files.
lua:  in streaming api, indicate open/close

The SCStreamingBuffer call now also returns two booleans:
    data, data_open, data_close = SCStreamingBuffer()

The first indicates this is the first data of this type for this
TCP session or HTTP transaction.

The second indicates this is the last data.

Ticket #1317.
pfring: fixes memleaks

This fixes some memory leaks
Bug #1184
pcre: fix var capture for non relative matches

Var capture setup depended on the match being relative due to a logic
error.