[PATCH] support RFC4525 modify+increment extension

[Andreas H. <aha...@te...>]

Attached. Simple example:

print "Before:"
print ld.search_s(BASE, ldap.SCOPE_SUBTREE, "(objectClass=sambaUnixIdPool)", ['uidNumber'])

modlist = [(ldap.MOD_INCREMENT, "uidNumber", "1")]
res = ld.modify_s("cn=unixIdPool,dc=example,dc=com", modlist)

print "After:"
print ld.search_s(BASE, ldap.SCOPE_SUBTREE, "(objectClass=sambaUnixIdPool)", ['uidNumber'])

Output:
$ ./modify+increment.py
Before:
[('cn=unixIdPool,dc=example,dc=com', {'uidNumber': ['1042']})]
After:
[('cn=unixIdPool,dc=example,dc=com', {'uidNumber': ['1043']})]