ruby: slicc: remove member buffer_expr from Var class
This was added by changeset 51f40b101a56. Instead, buffer_expr would now be
associated with the InPort class.

slicc: support for multiple message types on the same buffer

This patch allows SLICC protocols to use more than one message type with a
message buffer. For example, you can declare two in ports as such:

in_port(ResponseQueue_in, ResponseMsg, responseFromDir, rank=3) { ... }
in_port(tgtResponseQueue_in, TgtResponseMsg, responseFromDir, rank=2) { ... }

ruby: slicc: donot prefix machine name to variables
This changeset does away with prefixing of member variables of state machines
with the identity of the machine itself.

Ruby: Modify Scons so that we can put .sm files in extras
Also allows for header files which are required in slicc generated
code to be in a directory other than src/mem/ruby/slicc_interface.

slicc: Pure python implementation of slicc.
This is simply a translation of the C++ slicc into python with very minimal
reorganization of the code. The output can be verified as nearly identical
by doing a "diff -wBur".

Slicc can easily be run manually by using util/slicc