Add signed/fixedpoint properties (#140)

* declared intwidth, fracwidth, and is_signed UDPs

* fix boolean type name in UDP definition

* generate hwif fields with fixedpoint indices

* make "counter" and "encode" properties mutualy exclusive with signed/fixedpoint

* add signed/unsigned to hwif

* improved fixedpoint error messages, added validation tests

* added fixedpoint tests

* fixedpoint/signed not allowed for signal components

* added signed/fixedpoint UDP docs

* handle single-bit fixedpoint numbers

* fix too many positional arguments lint

* changed spelling of fixedpoint to fixed-point

* use "logic" in place of "unsigned logic"

* split signed and fixedpoint docs, added examples

* allow enums with is_signed=false

* split signed and fixedpoint implementations

* assorted nits picked

* updated is_signed validation unit test

docs/udps/intro.rst

@@ -60,3 +60,26 @@ To enable these UDPs, compile this RDL file prior to the rest of your design:
         - Enables an output strobe that is asserted on sw writes.
 
           See: :ref:`extended_swacc`.
+
+    *   - is_signed
+        - field
+        - boolean
+        - Defines the signedness of a field.
+
+          See: :ref:`signed`.
+
+    *   - intwidth
+        - field
+        - unsigned integer
+        - Defines the number of integer bits in the fixed-point representation
+          of a field.
+
+          See: :ref:`fixedpoint`.
+
+    *   - fracwidth
+        - field
+        - unsigned integer
+        - Defines the number of fractional bits in the fixed-point representation
+          of a field.
+
+          See: :ref:`fixedpoint`.