Fix more header-related warnings.

This fixes all current default warnings with GCC7 on Linux.  That does
not mean the code is anywhere close to clean.

rogue4/mach_dep.c

@@ -38,6 +38,11 @@
 #include <fcntl.h>
 #include <string.h>
 #include <errno.h>
+
+#ifdef CHECKTIME
+#include <unistd.h>
+#endif
+
 #include "rogue.h"
 
 int num_checks;		/* times we've gone over in checkout() */
@@ -266,9 +271,9 @@ checkout(int s)
 
 #ifdef CHECKTIME
 	checktime = (CHECKTIME * 60) / num_checks;
-#endif
 #ifdef SIGALRM
 	alarm(checktime);
+#endif
 #endif
 
 	chmsg(msgs[num_checks - 1], ((double) checktime / 60.0));

rogue4/mdport.c

@@ -43,6 +43,8 @@
 #undef MOUSE_MOVED
 #elif defined(__DJGPP__)
 #include <process.h>
+#else
+#include <sys/wait.h>
 #endif
 
 #ifdef HAVE_PWD_H
@@ -54,6 +56,9 @@
 #ifdef HAVE_UTMPX_H
 #include <utmpx.h>
 #endif
+#ifdef HAVE_ARPA_INET_H
+#include <arpa/inet.h>
+#endif
 
 #ifdef __INTERIX
 char *strdup(const char *s);
@@ -535,7 +540,7 @@ int md_endian = 0x01020304;
 unsigned long int
 md_ntohl(unsigned long int x)
 {
-#ifdef _WIN32
+#ifndef HAVE_ARPA_INET_H
     if ( *((char *)&md_endian) == 0x01 )
         return(x);
     else
@@ -551,7 +556,7 @@ md_ntohl(unsigned long int x)
 unsigned long int
 md_htonl(unsigned long int x)
 {
-#ifdef _WIN32
+#ifndef HAVE_ARPA_INET_H
     if ( *((char *)&md_endian) == 0x01 )
         return(x);
     else