RTEMS: Prefer int for int32_t

RTEMS: Prefer int for int32_t

Common systems like glibc and FreeBSD define int32_t to int.  This means
a lot of third party code works well in these cases:

  #include <stdint.h>

  void f(int32_t);

  void f(int);

  void g(int32_t *);

  void h(void)
  {
    int i;
    g(&i);
  }

On RTEMS you got however in C

  test.c:5:6: error: conflicting types for 'f'
    void f(int);
        ^
  test.c:3:6: note: previous declaration of 'f' was here
    void f(int32_t);
        ^
  test.c: In function 'h':
  test.c:12:4: warning: passing argument 1 of 'g' from incompatible
  pointer type [-Wincompatible-pointer-types]
    g(&i);
      ^
  test.c:7:6: note: expected 'int32_t * {aka long int *}' but argument
  is of type 'int *' void g(int32_t *);

and C++

  test.c: In function 'void h()':
  test.c:12:4: error: invalid conversion from 'int*' to 'int32_t* {aka
  long int*}' [-fpermissive]
    g(&i);
      ^~
  test.c:7:6: note:   initializing argument 1 of 'void g(int32_t*)'
    void g(int32_t *);
      ^

This was due to a Newlib speciality which uses long for int32_t if long
is a 32-bit type.  To ease the use of third party software in RTEMS we
override this Newlib option now and use int for int32_t if int is a
32-bit type.

gcc/
	* config/rtems.h (STDINT_LONG32): Define.

From-SVN: r261582