Returns the convertible integer type of the given +type+. You may
optionally specify additional +headers+ to search in for the +type+.
_Convertible_ means actually same type, or typedefed from same type.
If the +type+ is a integer type and _convertible_ type is found,
following macros are passed as preprocessor constants to the
compiler using the +type+ name, in uppercase.
* 'TYPEOF_', followed by the +type+ name, followed by '=X' where 'X'
is the found _convertible_ type name. * 'TYP2NUM' and 'NUM2TYP,
where 'TYP' is the +type+ name in uppercase with replacing '_t'
suffix with 'T', followed by '=X' where 'X' is the macro name to
convert +type+ to +Integer+ object, and vice versa.
For example, if foobar_t is defined as unsigned long, then
convertible_int("foobar_t") would return "unsigned long", and define
macros:
#define TYPEOF_FOOBAR_T unsigned long
#define FOOBART2NUM ULONG2NUM
#define NUM2FOOBART NUM2ULONG