proc,service: export declaration line of variables

Adds a field, DeclLine, to Variable containing the declaration line
number of the variable.

service/api/types.go

@@ -227,6 +227,8 @@ type Variable struct {
 
 	// LocationExpr describes the location expression of this variable's address
 	LocationExpr string
+	// DeclLine is the line number of this variable's declaration
+	DeclLine int64
 }
 
 // LoadConfig describes how to load values from target's memory