Add missing standard header includes spotted by gcc 4

c/scheme48vm-prelude.h

@@ -1,5 +1,6 @@
 #include <stdlib.h>
 #include <stdio.h>
+#include <string.h> /* memcpy, strlen */
 
 #include "c-mods.h"
 #include "write-barrier.h"

ps-compiler/compile-gc.scm

@@ -13,6 +13,7 @@
 	     "../scheme/vm/gc-package-defs.scm")
 	   's48-heap-init
 	   "../scheme/vm/scheme48heap.c"
-	   '(header "#include \"scheme48vm.h\"")
+           '(header "#include <string.h>")
+           '(header "#include \"scheme48vm.h\"")
 	   ;'(copy (heap walk-over-type-in-area))
 	   '(integrate (real-copy-object s48-trace-locations!)))))

scsh/libscsh.c

@@ -4,6 +4,7 @@
 
 #include <stdarg.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include "scheme48.h"
 #include "libscsh.h"
 #include "sysdep.h"

scsh/scsh-tramp.c

@@ -37,6 +37,7 @@
 
 #include <errno.h>
 #include <unistd.h>
+#include <stdlib.h> 
 
 #ifndef VM
 #define VM "/usr/local/lib/scsh/scshvm"

scsh/scsh_aux.c

@@ -3,7 +3,7 @@
 
 #include "scsh_aux.h"
 #include <signal.h>
-
+#include <stdio.h>
 
 int main(int argc, char* argv[]){
   int signr = atoi(argv[1]);