Update CHANGELOG and README

Signed-off-by: David Shah <dave@ds0.me>

README.md

@@ -371,6 +371,11 @@ Verilog Attributes and non-standard features
   for example, to specify the clk-to-Q delay of a flip-flop for consideration
   during techmapping.
 
+- The frontend sets attributes ``always_comb``, ``always_latch`` and
+  ``always_ff`` on processes derived from SystemVerilog style always blocks
+  according to the type of the always. These are checked for correctness in
+  ``proc_dlatch``.
+
 - In addition to the ``(* ... *)`` attribute syntax, Yosys supports
   the non-standard ``{* ... *}`` attribute syntax to set default attributes
   for everything that comes after the ``{* ... *}`` statement. (Reset