Prep for release (OpenLDAP 2.5.6)

CHANGES

 OpenLDAP 2.5 Change Log
 
-OpenLDAP 2.5.6 Engineering
+OpenLDAP 2.5.6 Release (2021/07/27)
 	Fixed libldap buffer overflow (ITS#9578)
 	Fixed libldap missing mutex unlock on connection alloc failure (ITS#9590)
 	Fixed lloadd cn=config olcBkLloadClientMaxPending setting (ITS#8747)

build/version.var

@@ -15,9 +15,9 @@
 ol_package=OpenLDAP
 ol_major=2
 ol_minor=5
-ol_patch=X
-ol_api_inc=20505
+ol_patch=6
+ol_api_inc=20506
 ol_api_current=1
-ol_api_revision=0
+ol_api_revision=1
 ol_api_age=1
-ol_release_date="2021/06/03"
+ol_release_date="2021/07/27"