sim: ppc: avoid shadowing errno

If the OS headers define the "errno" symbol, it breaks some of these
funcs that were using "int errno" itself.  Rename local vars to "err"
to avoid that, and delete the old "extern int errno".

sim/ppc/emul_unix.c

@@ -124,10 +124,6 @@ int getrusage();
 #include <stdlib.h>
 #include <time.h>
 
-#if defined(BSD) && !defined(errno) && (BSD < 199306)	/* here BSD as just a bug */
-extern int errno;
-#endif
-
 #ifndef STATIC_INLINE_EMUL_UNIX
 #define STATIC_INLINE_EMUL_UNIX STATIC_INLINE
 #endif