Update CHANGES (releng for 2.3).
Update CHANGES (releng for 2.3).

Change-Id: Ifde07e2134555c8439ddadd68052addc3a9e159c
Signed-off-by: Piotr Sikora <321b1a11e6b8c7ca12f1b0b438664e52a48b555e@frickle.com>

FRiCKLE/ngx_cache_purge,ainoya/ngx_cache_purge,FRiCKLE/ngx_cache_purge,lilien1010/ngx_cache_purge,lilien1010/ngx_cache_purge,ainoya/ngx_cache_purge