The following routines in Tcl's public interface, `tcl.h`, make
use of the ''mp_int'' type:

   * '''Tcl_NewBignumObj'''(''mp_int *'')
   * '''Tcl_DbNewBignumObj'''(''mp_int *'', ''const char *'', ''int'')
   * '''Tcl_SetBignumObj'''(''Tcl_Obj *'', ''mp_int *'')
   * '''Tcl_GetBignumFromObj'''(''Tcl_Interp *'', ''Tcl_Obj *'', ''mp_int *'')
   * '''Tcl_TakeBignumFromObj'''(''Tcl_Interp *'', ''Tcl_Obj *'', ''mp_int *'')
   * '''Tcl_InitBignumFromDouble'''(''Tcl_Interp *'', ''double'', ''mp_int *'')

Tcl's public header, `tcl.h` also includes these declarations:

===
#ifndef MP_INT_DECLARED
typedef struct mp_int mp_int;
#define MP_INT_DECLARED
#endif
#ifndef MP_DIGIT_DECLARED
typedef unsigned long mp_digit;
#define MP_DIGIT_DECLARED
#endif
===

which allows the compiler to make sense of the function declarations.

Callers of those functions must be able to allocate an ''mp_int''
struct so they can pass its address in.  In order to do this a
definition of the ''mp_int'' struct has to be in scope, but Tcl's
public header `tcl.h` does not provide one.

Q1:  What header file are callers of these routines expected
to #include to get a suitable ''mp_int'' definition in scope?

Q2: