Fix newlib H8/300 bits for C99/gcc-14

Similar to other patches.  This adds a missing prototype and #include to some
H8/300 specific code in newlib.  Pushed to the trunk given Jeff J's
pre-approval for these kinds of changes.

newlib/libc/sys/h8300hms/sbrk.c

@@ -1,8 +1,10 @@
 #include <_ansi.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <stdlib.h>
 
 register char *stack_ptr asm ("sp");
+extern int _write (int, char *, int);
 
 caddr_t 
   _sbrk(incr)