Prep for release (OpenLDAP 2.5.7)

CHANGES

 OpenLDAP 2.5 Change Log
 
-OpenLDAP 2.5.7 Engineering
+OpenLDAP 2.5.7 Release (2021/08/18)
 	Fixed lloadd client state tracking (ITS#9624)
 	Fixed slapd bconfig to canonicalize structuralObjectclass (ITS#9611)
 	Fixed slapd-ldif duplicate controls response (ITS#9497)

build/version.var

@@ -15,9 +15,9 @@
 ol_package=OpenLDAP
 ol_major=2
 ol_minor=5
-ol_patch=X
-ol_api_inc=20506
+ol_patch=7
+ol_api_inc=20507
 ol_api_current=1
-ol_api_revision=1
+ol_api_revision=2
 ol_api_age=1
-ol_release_date="2021/07/27"
+ol_release_date="2021/08/18"