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.

tests2/40_stdio.c

@@ -0,0 +1,52 @@
+#include <stdio.h>
+
+int main()
+{
+   FILE *f = fopen("fred.txt", "w");
+   fwrite("hello\nhello\n", 1, 12, f);
+   fclose(f);
+
+   char freddy[7];
+   f = fopen("fred.txt", "r");
+   if (fread(freddy, 1, 6, f) != 6)
+      printf("couldn't read fred.txt\n");
+
+   freddy[6] = '\0';
+   fclose(f);
+
+   printf("%s", freddy);
+
+   char InChar;
+   char ShowChar;
+   f = fopen("fred.txt", "r");
+   while ( (InChar = fgetc(f)) != EOF)
+   {
+      ShowChar = InChar;
+      if (ShowChar < ' ')
+         ShowChar = '.';
+
+      printf("ch: %d '%c'\n", InChar, ShowChar);
+   }
+   fclose(f);
+
+   f = fopen("fred.txt", "r");
+   while ( (InChar = getc(f)) != EOF)
+   {
+      ShowChar = InChar;
+      if (ShowChar < ' ')
+         ShowChar = '.';
+
+      printf("ch: %d '%c'\n", InChar, ShowChar);
+   }
+   fclose(f);
+
+   f = fopen("fred.txt", "r");
+   while (fgets(freddy, sizeof(freddy), f) != NULL)
+      printf("x: %s", freddy);
+
+   fclose(f);
+
+   return 0;
+}
+
+/* vim: set expandtab ts=4 sw=3 sts=3 tw=80 :*/