Reduced the number of INT_FATAL() cases in cast_code.cpp.
Changed (u)int-to-c_string coercions in cast_code.cpp to use new istrFromUserInt/Uint functions.
Replaced int_value() with v_int64, ditto uint, in compiler/ifa/*
Defuturized param-uint-to-param-string.future
Merge pull request #1073 from vasslitvinov/improve--cast_code.cpp

Fixed param casts from 'int(64)' & 'uint(?)' to 'c_string'.

Before, only 32 bits were considered and they were treated as signed.
E.g. param cast uint64->c_string was:

       to->v_string = istr(from->uint_value()); break;

now it is:

       to->v_string = istrUserUint(from->v_uint64); break;

For that I introduced istrUserUint() and istrUserInt()
that are like istr() except:

* they accept "long long unsigned int" and "long long int", resp.
  (I use them for smaller-sized arguments, too)

* their sprintf format is "%llu" and "%lld", resp.


While there:

* Removed a bunch of extraneous cases like this:

   case XXX: INT_FATAL("Illegal case in coerce_immediate switch statement"); break;

  when there was a 'default' case with the same INT_FATAL().

* Replaced uint_value() with v_uint64 and analogously for int64,
  for clarity/consistency. Only in compiler/ifa/*.

* Defuturized param-uint-to-param-string.future.


Reviewed by Tom.