try to reduce some Amiga cross-compile warnings

sys/amiga/amidos.c

@@ -450,7 +450,11 @@ fopenp(const char *name, const char *mode)
 static BPTR OrgDirLock = NO_LOCK;
 
 int
-chdir(char *dir)
+chdir(
+#ifdef CROSS_TO_AMIGA
+      const
+#endif
+      char *dir)
 {
     extern char orgdir[];
 

sys/amiga/amidos.p

@@ -31,10 +31,10 @@ void getreturn(const char *);
 #ifndef msmsg
 void msmsg( const char *, ... );
 #endif
-#if !defined(__SASC_60) && !defined(_DCC)
+#if !defined(__SASC_60) && !defined(_DCC) && !defined(CROSS_TO_AMIGA)
 int chdir(char *);
 #endif
-#ifndef	strcmpi
+#ifndef        strcmpi
 int strcmpi(char * , char *);
 #endif
 #if !defined(memcmp) && !defined(AZTEC_C) && !defined(_DCC) && !defined(__GNUC__)

sys/amiga/amiwind.c

@@ -891,6 +891,10 @@ amii_loadlib(void)
 {
 }
 
+#ifdef CROSS_TO_AMIGA
+extern void Abort(long) NORETURN;
+#endif
+
 /* fatal error */
 /*VARARGS1*/
 void error