LDAP.pod: add note about IO::Socket::IP and Timeout
Control/Paged.pm: remove superfluous ( from sample code
Control.pm: add a bit of general information about controls
Control.pm: separate SEE ALSO links in POD by commas
Control.pm: add Net::LDAP::Control::Relax to POD
Control.pm: better / more complete example in POD
Message.pod: consolidate description of control()
t/60cancel.t: add explanation about potential cause of failure
LDIF.pm: refactor - new method _read_attribute_value()

Only use it when necessary, as otherwise it slows down
reading by an unacceptable factor of 4.
LDIF.pm: re-factor handling DNs when reading
t/00ldif-entry.t: use current methods instead of deprecated ones
LDIF.pm: refactor - make _error() return undef/empty list, adapt callers
LDIF.pm: error checks when reading changetype: delete
LDIF.pm: coding style harmonization

- line break before else
- push(@x,$y) instead of push @x, $y
- more if / unless as postfix operators
- braces around the test-argument of if / unless
- 2-character indent
- space police
LDIF.pm: refactor - simplify _write_entry

Simplify the 'changetype: modify' case in _write_entry.
LDIF.pm: refactor - simplify _read_entry
LDIF.pm: set error when write fails
Handle SASL security layers correctly on rebind.

According to the RFC, if we are using a SASL security layer, then we
rebind and negotiate a new security layer, the new layer replaces the
old. If, on the other hand, the rebind doesn't negotiate a security
layer, then the old layer remains in place. Previously Net::LDAP was
attempting to apply the new layer (if any) on top of the old layer,
which is incorrect.

Rebind was also failing if a security layer had previously been
negotiated since the security-layer filehandle doesn't support socket
operations. Since we now need to keep the raw (TCP or SSL) filehandle
around anyway, we can do the socket operations on that instead.
LDAP.pm: set net_ldap_rawsocket centrally

Set net_ldap_rawsocket centrally once in new() instead in the various
connect_ldap*() methods.
Bind.pm: re-factor (re-)negotiating a new layer

Make it more easily readable, like the previously existing version.