mxIs* functions now return bool

[Rik]

9/10/16
I've been working on improving the MEX interface in Octave.  One of the
things I noticed is that the predicate tests in Matlab are all returning a
bool, whereas in Octave they return an int.  A predicate test might be
something like mxIsScalar or mxIsComplex.  Does anyone see a problem with
changing the function prototypes to return bool?

extern OCTINTERP_API int mxIsComplex (const mxArray *ptr);
=>
extern OCTINTERP_API bool mxIsComplex (const mxArray *ptr);

One of the things I don't understand is that the C language didn't have a
bool type until C99, and even then it was necessary to #include <stdbool.h>
in order to access it.  However, I accidentally coded mxIsScalar to return
bool and it has compiled correctly.  The only thing I see at the top of
mexproto.h is

#if defined (__cplusplus)
#  include <cstdlib>
extern "C" {
#else
#  include <stdlib.h>
#endif

When I run 'mex -v ...' I can see that the compiler is gcc, not g++, so I
don't think the first branch is being taken.  Should I worry and add the
include for stdbool.h when compiling with a straight C compiler?

--Rik