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.

tcc.h

@@ -400,7 +400,11 @@ typedef union CValue {
     double d;
     float f;
     uint64_t i;
-    struct CString *cstr;
+    struct {
+        int size;
+        const void *data;
+        void *data_allocated;
+    } str;
     int tab[LDOUBLE_SIZE/4];
 } CValue;