Pedantically type-cast integer comparisons

The latest versions of the GNU Compiler Collection complain about signed
and unsigned integer comparisons when run with the "-Wextra" flag.  Keep
those compilers happy.

src/exch.c

@@ -210,7 +210,7 @@ void exchange_stock (void)
 		}
 
 		for (i = 0, found = false; keycode_company[i] != L'\0'; i++) {
-		    if (keycode_company[i] == key) {
+		    if (keycode_company[i] == (wchar_t) key) {
 			found = true;
 			if (company[i].on_map) {
 			    selection = i;

src/intf.c

@@ -1268,7 +1268,7 @@ void mkchstr_conv (chtype *restrict chbuf, int chbufsize,
 	// Yes, we want to convert a wide NUL, too!
 	n = xwcrtomb(convbuf, *wcbuf, &mbstate);
 
-	if (chbufsize > endsize + n) {
+	if (chbufsize > (int) endsize + (int) n) {
 	    for (p = convbuf; n > 0; n--, p++, chbuf++, chbufsize--) {
 		if (*p == '\0' || *p == '\n') {
 		    /* This code assumes '\n' can never appear in a

src/move.c

@@ -292,7 +292,7 @@ selection_t get_move (void)
 		}
 
 		for (i = 0, found = false; keycode_game_move[i] != L'\0'; i++) {
-		    if (keycode_game_move[i] == key) {
+		    if (keycode_game_move[i] == (wchar_t) key) {
 			found = true;
 			selection = i;
 

src/utils.c

@@ -747,7 +747,7 @@ char *unscramble (char *restrict dest, const char *restrict src,
 	apply_xor(dest, midxor, xorlen - SCRAMBLE_CRC_LEN, key);
 
 	// Convert the output to a C string
-	assert(size >= xorlen - SCRAMBLE_CRC_LEN + 1);
+	assert(size >= (size_t) xorlen - SCRAMBLE_CRC_LEN + 1);
 	dest[xorlen - SCRAMBLE_CRC_LEN] = '\0';
 
 	free(xorbuf);