Do not warn about shadowing parameters in functions without implementation

test/libsolidity/syntaxTests/scoping/name_shadowing_function_parameter_name_vs_contract.sol

@@ -0,0 +1,20 @@
+interface I {
+    function f(uint I) external;         // OK
+}
+
+library L {
+    function f(uint L) public pure {}    // warning
+}
+
+abstract contract A {
+    function f(uint A) public pure {}    // warning
+    function g(uint A) public virtual;   // OK
+}
+
+contract C {
+    function f(uint C) public pure {}    // warning
+}
+// ----
+// Warning 2519: (91-97): This declaration shadows an existing declaration.
+// Warning 2519: (168-174): This declaration shadows an existing declaration.
+// Warning 2519: (283-289): This declaration shadows an existing declaration.

test/libsolidity/syntaxTests/scoping/name_shadowing_function_parameter_vs_its_function.sol

@@ -0,0 +1,5 @@
+contract C {
+    function f(uint f) pure public {}
+}
+// ----
+// Warning 2519: (28-34): This declaration shadows an existing declaration.