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.

tests2/38_multiple_array_index.c

@@ -0,0 +1,32 @@
+#include <stdio.h>
+
+int main()
+{
+   int a[4][4];
+   int b = 0;
+   int x;
+   int y;
+
+   for (x = 0; x < 4; x++)
+   {
+      for (y = 0; y < 4; y++)
+      {
+         b++;
+         a[x][y] = b;
+      }
+   }
+
+   for (x = 0; x < 4; x++)
+   {
+      printf("x=%d: ", x);
+      for (y = 0; y < 4; y++)
+      {
+         printf("%d ", a[x][y]);
+      }
+      printf("\n");
+   }
+
+   return 0;
+}
+
+/* vim: set expandtab ts=4 sw=3 sts=3 tw=80 :*/