[swift-parse-test] Add -skip-bodies option

This is no-op for SwiftParser. Also add a sanity check test file.

test/Misc/parse_test.swift

@@ -0,0 +1,8 @@
+// REQUIRES: swift_swift_parser
+// RUN: %swift-parse-test -swift-parser -lib-parse -skip-bodies -n 2 %s
+
+struct S {
+  func foo() {
+    print(1)
+  }
+}