tests: Added numerous tests.

The tests are taken almost verbatim from the open source project PicoC. It can
be found at https://code.google.com/p/picoc/.

The tests range from very simple/trivial ones to more complicated. My view is
that the more tests the better. Without tests like this I was very reluctant to
make any changes to tcc for the fear of breaking things.

The tests pass on Win32, OSX, Linux x86 and x86_64. One or two tests fail on
each platform due to differences in the runtime library.

tests2/47_switch_return.c

@@ -0,0 +1,24 @@
+#include <stdio.h>
+
+void fred(int x)
+{
+   switch (x)
+   {
+      case 1: printf("1\n"); return;
+      case 2: printf("2\n"); break;
+      case 3: printf("3\n"); return;
+   }
+
+   printf("out\n");
+}
+
+int main()
+{
+   fred(1);
+   fred(2);
+   fred(3);
+
+   return 0;
+}    
+
+/* vim: set expandtab ts=4 sw=3 sts=3 tw=80 :*/