Merge pull request #1943 from YosysHQ/dave/fix-1919

ast: Fix handling of identifiers in the global scope

tests/various/global_scope.ys

@@ -0,0 +1,18 @@
+read_verilog -sv <<EOT
+parameter A = 10;
+parameter B = A;
+
+typedef enum {
+	CONST_A = A,
+	CONST_B = A+1
+} enum_t;
+
+module top(output [3:0] q, output [3:0] r);
+assign q = 10;
+assign r = CONST_B;
+endmodule
+EOT
+
+hierarchy -top top
+sat -verify -prove q 10 top
+sat -verify -prove r 11 top