Make ekermit compile on NetBSD:

* Add several #includes of standard headers in platform.h.
* #undef X_OK in platform.h.  It's defined in the standard <access.h>,
  but also used in the local "kermit.h" for a differentpurpose.
* Declare {struct k_data}.dbf as a function returning void, not int,
  to match the way it's used.

external/bsd/ekermit/dist/kermit.h

@@ -383,7 +383,7 @@ struct k_data {                         /* The Kermit data structure */
     int (*readf)(struct k_data *);	         /* read-file function  */
     int (*writef)(struct k_data *,UCHAR *, int); /* write-file function */
     int (*closef)(struct k_data *,UCHAR,int);    /* close-file function */
-    int (*dbf)(int,UCHAR *,UCHAR *,long);  /* debug function */
+    void (*dbf)(int,UCHAR *,UCHAR *,long);  /* debug function */
     UCHAR * zinbuf;			/* Input file buffer itself */
     int zincnt;				/* Input buffer position */
     int zinlen;				/* Length of input file buffer */

external/bsd/ekermit/dist/platform.h

@@ -1,8 +1,14 @@
 /* Unix platform.h for EK */
 
+#include <ctype.h>
+#include <errno.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
 #include <sys/stat.h>
 
+#undef X_OK	/* namespace collision between kermit.h and unistd.h */
+
 #ifndef IBUFLEN
 #define IBUFLEN  4096			/* File input buffer size */
 #endif /* IBUFLEN */