Change the way struct CStrings are handled.

A CString used to be copied into a token string, which is an int array.
On a 64-bit architecture the pointers were misaligned, so ASan gave
lots of warnings. On a 64-bit architecture that required memory
accesses to be correctly aligned it would not work at all.

The CString is now included in CValue instead.

TODO

@@ -36,7 +36,6 @@ Portability:
 
 - it is assumed that int is 32-bit and sizeof(int) == 4
 - int is used when host or target size_t would make more sense
-- struct CString is written into an int array and ends up misaligned
 - TCC handles target floating-point (fp) values using the host's fp
   arithmetic, which is simple and fast but may lead to exceptions
   and inaccuracy and wrong representations when cross-compiling