tolerate escaped vendor comments within macros

src/Language/SystemVerilog/Parser/Preprocess.hs

@@ -546,6 +546,10 @@ preprocessInput = do
         '/' : '*' : _ -> removeThrough "*/"
         '`' : '"' : _ -> handleBacktickString
         '"' : _ -> handleString
+        '/' : '`' : '`' : '*' : _ ->
+            if null macroStack
+                then consume
+                else removeThrough "*``/"
         '`' : '`' : _ -> do
             if null macroStack
                 then do

test/error/stray_escaped_vendor_comment.sv

@@ -0,0 +1,4 @@
+// pattern: Parse error
+module top;
+    /``* some awful garbage *``/
+endmodule

test/lex/macro_vendor_comment.sv

@@ -0,0 +1,4 @@
+`define YUCK /``* some awful garbage *``/
+module top;
+    `YUCK
+endmodule