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.

tests2/41_hashif.c

@@ -0,0 +1,85 @@
+#include <stdio.h>
+
+int main()
+{
+   printf("#include test\n");
+
+#if 1
+#if 0
+   printf("a\n");
+#else
+   printf("b\n");
+#endif
+#else
+#if 0
+   printf("c\n");
+#else
+   printf("d\n");
+#endif
+#endif
+
+#if 0
+#if 1
+   printf("e\n");
+#else
+   printf("f\n");
+#endif
+#else
+#if 1
+   printf("g\n");
+#else
+   printf("h\n");
+#endif
+#endif
+
+#define DEF
+
+#ifdef DEF
+#ifdef DEF
+   printf("i\n");
+#else
+   printf("j\n");
+#endif
+#else
+#ifdef DEF
+   printf("k\n");
+#else
+   printf("l\n");
+#endif
+#endif
+
+#ifndef DEF
+#ifndef DEF
+   printf("m\n");
+#else
+   printf("n\n");
+#endif
+#else
+#ifndef DEF
+   printf("o\n");
+#else
+   printf("p\n");
+#endif
+#endif
+
+#define ONE 1
+#define ZERO 0
+
+#if ONE
+#if ZERO
+   printf("q\n");
+#else
+   printf("r\n");
+#endif
+#else
+#if ZERO
+   printf("s\n");
+#else
+   printf("t\n");
+#endif
+#endif
+
+   return 0;
+}
+
+/* vim: set expandtab ts=4 sw=3 sts=3 tw=80 :*/