decode: replace decode_insn_i[`OR1K_OPCODE_SELECT] with opc_insn

and put spaces around ==
decode: use more descriptive names for branch signals
icache: (temporary) disable out of refill cacheline accesses.

This caused a regression on an Atlys board when booting
the linux kernel.
Exclude gpr accessor functions from synthesis

Synplify pro fails when it encounters set_gpr.
Rename mor1kx.txt to mor1kx.asciidoc
Update Makefile, s/\.txt/.asciidoc/g
replace missing'
Merge pull request #3 from ysangkok/patch-1

Rename ASCIIDOC sources to .asciidoc so that they are viewable online with Github
move all decode to execute signal registering to a seperate module

Currently, only the cappuccino pipeline implementation register
the signals from decode stage into execute stage,
(pronto)espresso does not have a seperate execute stage.

So, instead of trying to accomodate for both use cases in the
mor1kx_decode module, break out the registering of the signals
and all cappuccino specific logic into a seperate
mor1kx_decode_execute_cappuccino module.
If (or when) a new pipeline implementation arises that would
benefit from using this module, it should be determined whether
the _cappuccino in the name can be dropped (i.e., is it generic
enough to be used across pipeline implementations).

Also prefix all output signals coming from mor1kx_decode with
decode_, to make it clear what their origin is in the cpu_xxx
modules.