Core: changed ngx_queue_sort() to use merge sort. This improves nginx startup times significantly when using very large number of locations due to computational complexity of the sorting algorithm being used: insertion sort is O(n*n) on average, while merge sort is O(n*log(n)). In particular, in a test configuration with 20k locations total startup time is reduced from 8 seconds to 0.9 seconds. Prodded by Yusuke Nojima, https://mailman.nginx.org/pipermail/nginx-devel/2023-September/NUL3Y2FPPFSHMPTFTL65KXSXNTX3NQMK.html

--- a/src/core/ngx_queue.h
+++ b/src/core/ngx_queue.h
@@ -47,6 +47,9 @@ struct ngx_queue_s {
     (h)->prev = x
 
 
+#define ngx_queue_insert_before   ngx_queue_insert_tail
+
+
 #define ngx_queue_head(h)                                                     \
     (h)->next