stop silly warnings

These both created warnings about potential truncation that in an of themselves
were already bogus, but were turned into errors by zealous distro compiler
defaults.
The new code is annoying and marginally pointless, but... alas.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

core/uemis-downloader.cpp

@@ -285,10 +285,12 @@ static char *build_filename(const char *path, const char *name)
 	int len = strlen(path) + strlen(name) + 2;
 	char *buf = (char *)malloc(len);
 #if WIN32
-	snprintf(buf, len, "%s\\%s", path, name);
+	l = snprintf(buf, len, "%s\\%s", path, name);
 #else
-	snprintf(buf, len, "%s/%s", path, name);
+	l = snprintf(buf, len, "%s/%s", path, name);
 #endif
+	if(l < 0 or l > len)
+		printf("this compiler is broken -- snprintf returned %d\n", l);
 	return buf;
 }
 
@@ -517,14 +519,10 @@ static void uemis_increased_timeout(int *timeout)
 
 static char *build_ans_path(const char *path, int filenumber)
 {
-	char *intermediate, *ans_path, fl[13];
+	char *intermediate, *ans_path, fl[15];
 
-	/* Clamp filenumber into the 0..9999 range. This is never necessary,
-	 * as filenumber can never go above UEMIS_MAX_FILES, but gcc doesn't
-	 * recognize that and produces very noisy warnings. */
-	filenumber = filenumber < 0 ? 0 : filenumber % 10000;
-
-	snprintf(fl, 13, "ANS%d.TXT", filenumber);
+	uint16_t fn =  (filenumber < 0 || filenumber > UEMIS_MAX_FILES) ? 0 : filenumber;
+	snprintf(fl, 15, "ANS%u.TXT", fn);
 	intermediate = build_filename(path, "ANS");
 	ans_path = build_filename(intermediate, fl);
 	free(intermediate);