* Use signed output in LargeParamExecutionTest

Change the Verilog used in LargeParamExecutionTest to match its
ExtModule specification. An ExtModule with an SInt port should map to
a separate Verilog module with a signed port and this is disjoint from
an ExtModule with a UInt port.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

* Error on ExtModules w/ same defname, diff. ports

Adds a high form check to ensure that external modules that have the
same defname also have exactly the same ports.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Emit Verilog IntParams that fit in 32-bits as Integer literals

When constructing the black box helper file list (firrtl_black_box_resource_files.f), filter out Verilog header files (*.vh) - Fixes #917

Escape raw params using \'

* Rename implict module "clk" input to "clock".
This doesn't rename all the "self-contained" test instances.
nor the memory "clk" enables,
nor the implict module "clk"s in the regress .fir files.

* Consistency: rename implict module "clk" input to "clock" in "self-contained" test instances.
This doesn't rename the memory "clk" enables, nor the implict module "clk"s in the regress .fir files.

Replace with more sensible comment to see LICENSE rather than including the
whole license in every file

While unsafe, this supports Verilog parameter types.
Tests now require Verilator 3.884+ to pass.

Adds support for Integer, Double/Real, and String parameters in external
modules. Also add name field to extmodules so that emitted name can be
different from Firrtl name. This is important because parameterized extmodules
will frequently have differing IO even though they need to be emitted as
instantiating the same Verilog module.