correct a few minor typos in sys

sys/unix/unixmain.c

@@ -623,7 +623,7 @@ early_options(int *argc_p, char ***argv_p, char **hackdir_p)
 
     /*
      * Both *argc_p and *argv_p account for the program name as (*argv_p)[0];
-     * local argc and argv impicitly discard that (by starting 'ndx' at 1).
+     * local argc and argv implicitly discard that (by starting 'ndx' at 1).
      * argcheck() doesn't mind, prscore() (via scores_only()) does (for the
      * number of args it gets passed, not for the value of argv[0]).
      */

sys/windows/build-nmake.txt

@@ -62,7 +62,7 @@ Building
 Two different versions of NetHack will be built for Windows from the
 command line using the Makefile approach:
     A tty port utilizing the Win32 Console I/O subsystem Console,
-    and a curses interface in an executabled called NetHack.exe.
+    and a curses interface in an executable called NetHack.exe.
         NetHack
     A Win32 native port built on the Windows API Graphical NetHack,
     and graphical curses in an executable called NetHackW.exe.

sys/windows/windsys.c

@@ -827,9 +827,9 @@ get_executable_path(void)
     path_buffer[length] = '\0';
 #endif
 
-    char *seperator = strrchr(path_buffer, PATH_SEPARATOR);
-    if (seperator)
-        *seperator = '\0';
+    char *separator = strrchr(path_buffer, PATH_SEPARATOR);
+    if (separator)
+        *separator = '\0';
 
     path_buffer_set = TRUE;
     return path_buffer;