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.

tests2/10_pointer.expect

@@ -0,0 +1,8 @@
+a = 42
+bolshevic.a = 12
+bolshevic.b = 34
+bolshevic.c = 56
+tsar->a = 12
+tsar->b = 34
+tsar->c = 56
+bolshevic.b = 34