make the SMB2 negotiated read and write size settable in smb.conf

parametic options:

  smb2:max read size = NNN  
  smb2:max write size = NNN

The defaults are 65536, which is what Vista sets, and what we
previously set
(This used to be commit 9e60164cae42b5dd95720e48301a2ac57e95482a)

source4/setup/provision

@@ -35,6 +35,8 @@ from samba.provision import (provision,
                              FILL_FULL, FILL_NT4SYNC,
                              FILL_DRS)
 
+# how do we make this case insensitive??
+
 parser = optparse.OptionParser("provision [options]")
 sambaopts = options.SambaOptions(parser)
 parser.add_option_group(sambaopts)