Fix v850 libgloss for c99/gcc-14

So the prior patch for sysnecv850 was in newlib.  This time we're fixing v850
bits in libgloss.

Like other patches submitted recently, this converts implicit ints to explicit
ints, adds a missing prototype and header includes.

libgloss/v850/_exit.c

@@ -23,7 +23,7 @@ static void _do_dtors()
 }
 
 
-void _exit (n)
+void _exit (int n)
 {
   /* Destructors should be done earlier because they need to be done before the
      files are closed, but here is better than nowhere (and this balances the

libgloss/v850/getpid.c

@@ -9,7 +9,8 @@ int __trap0 (int function, int p1, int p2, int p3);
 
 #define TRAP0(f, p1, p2, p3) __trap0(f, (int)(p1), (int)(p2), (int)(p3))
 
-_getpid (n)
+int
+_getpid (int n)
 {
   return 1;
 }

libgloss/v850/isatty.c

@@ -9,8 +9,8 @@ int __trap0 (int function, int p1, int p2, int p3);
 
 #define TRAP0(f, p1, p2, p3) __trap0(f, (int)(p1), (int)(p2), (int)(p3))
 
-_isatty (fd)
-     int fd;
+int
+_isatty (int fd)
 {
   return 1;
 }

libgloss/v850/kill.c

@@ -10,6 +10,7 @@ int __trap0 (int function, int p1, int p2, int p3);
 
 #define TRAP0(f, p1, p2, p3) __trap0(f, (int)(p1), (int)(p2), (int)(p3))
 
+int
 _kill (pid, sig)
      pid_t pid;
      int sig;

libgloss/v850/read.c

@@ -9,6 +9,7 @@ int __trap0 (int function, int p1, int p2, int p3);
 
 #define TRAP0(f, p1, p2, p3) __trap0(f, (int)(p1), (int)(p2), (int)(p3))
 
+int
 _read (int file,
        char *ptr,
        int len)

libgloss/v850/sbrk.c

@@ -2,6 +2,9 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include "sys/syscall.h"
+#include <stdlib.h>
+
+extern int _write (int, char *, int);
 
 caddr_t
 _sbrk (int incr)