Resolve "[2.2.10 prerelease] Trying to load a folder as an addon causes a "bad cycle" error every time"

Closes #712 (closed)

I've added a call to qsort() at the end of getdirectoryfiles(), so that the "lumps" added via addfolder are sorted alphabetically.

src/d_main.c

@@ -1842,17 +1842,21 @@ static boolean check_top_dir(const char **path, const char *top)
 	return true;
 }
 
-static int cmp_strlen_desc(const void *a, const void *b)
+static int cmp_strlen_desc(const void *A, const void *B)
 {
-	return ((int)strlen(*(const char*const*)b) - (int)strlen(*(const char*const*)a));
+	const char *pA = A;
+	const char *pB = B;
+	size_t As = strlen(pA);
+	size_t Bs = strlen(pB);
+	return ((int)Bs - (int)As);
 }
 
 boolean D_IsPathAllowed(const char *path)
 {
-	const char *paths[] = {
+	char *paths[] = {
 		srb2home,
 		srb2path,
-		cv_addons_folder.string
+		cv_addons_folder.zstring
 	};
 
 	const size_t n_paths = sizeof paths / sizeof *paths;