libc_server: make 64-bit safe

If we run on a 64-bit Linux kernel, we will have to replace 32-bit
pointers with 64-bit pointers. Make param_t always 64 bits, then the
payload doesn't need to care if that is the case or not.

libc_server.c

@@ -46,7 +46,7 @@ struct newlib_stat {
   /* uid_t */   unsigned short st_uid;
   /* gid_t */   unsigned short st_gid;
   /* dev_t */   unsigned short st_rdev;
-  /* off_t */   long           st_size;
+  /* off_t */   int32_t        st_size;
 };
 
 struct newlib_timeval {

libc_server.h

@@ -8,13 +8,7 @@
 #error INT_MAX/LONG_MAX not defined
 #endif
 
-// Find a data type that fits both pointers and integers.
-
-#if INT_MAX == LONG_MAX
-typedef uint32_t param_t;
-#else
 typedef uint64_t param_t;
-#endif
 
 enum libc_funcs {
     LIBC_WRITE,