Add 103_implicit_memmove testcase

which checks that a declaration after TCC implicitely declares
an internally used function (memmove here) doesn't create any problem.

tests/tests2/103_implicit_memmove.c

@@ -0,0 +1,20 @@
+/* Test that the memmove TCC is emitting for the struct copy
+   and hence implicitely declares can be declared properly also
+   later.  */
+struct S { int a,b,c,d, e[1024];};
+int foo (struct S *a, struct S *b)
+{
+  *a = *b;
+  return 0;
+}
+
+void *memmove(void*,void*,long);
+void foo2 (struct S *a, struct S *b)
+{
+  memmove(a, b, sizeof *a);
+}
+
+int main()
+{
+  return 0;
+}