Adds some more tests and groups all function call inheritance related together into single sub-directory.

test/libsolidity/semanticTests/functionCall/inheritance/call_base_explicit.sol

@@ -0,0 +1,14 @@
+contract Base {
+	function f(uint n) public returns (uint) {
+		return 2 * n;
+	}
+}
+
+contract Child is Base {
+	function g(uint n) public returns (uint) {
+		return Base.f(n);
+	}
+}
+// ----
+// g(uint256): 4 -> 8
+