Add a method for checking if the underlying stream is valid.

Remove unused variable

Revert "Add some const-ness to the protocol frame codec"

This reverts commit f8c2b459481209c3761a694baa6f38060dc9875a.

Don't use the specific translated name but use the macro for this

More const and moved the declaration of php_mysqlnd_scramble() to mysqlnd_auth.h

Bring consistency to the class by renaming the methods too (from the
old temporary name)

Add some const-ness to the protocol frame codec

mysqlnd refactoring:
- move MYSQLND_READ_BUFFER to own file

mysqlnd refactoring :
- move the command buffer out of the networking code to the protocol frame
codec.

- Remove dead macrom mysql_list_fields()
- Small optimizations here and there

MNDR:
- cleanup in mysqlnd_result.c
- switch from zend_ulong to size_t for lengths. Accordingly change
mysqli and pdo_mysql for this.

MNDR:
- less dereferencing in mysqlnd_ps . Dereference stmt->conn only once and
use a stack variable. Also make the source cleaner.

MNDR:
- move all data members from MYSQLND_PFC to MYSQLND_PFC_DATA

MNDR:
- move from char* + len to MYSQLND_STRING
- add some more const modifiers

MNDR:
- better name for MYSQLND_PPEC - MYSQLND_PFC (protocol frame codec)

MNDR:
- rename MYSQLND_NET to MYSQLND_PPEC (protocol packet envelope codec).
PPEC does only the encoding and decoding to the protocol frame.

MNDR:
- split MYSQLND_NET into MYSQLND_NET and MYSQLND_VIO
MYSQLND_NET is above MYSQLND_VIO. _NET takes care of protocol packet
counting (even with compressed), while VIO is just abou

MNDR:
- split MYSQLND_NET into MYSQLND_NET and MYSQLND_VIO
MYSQLND_NET is above MYSQLND_VIO. _NET takes care of protocol packet
counting (even with compressed), while VIO is just about the network
(or in case of windows, non-network, but PIPE) transport.

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MNDR:
- send_command and send_command_handle_response_* moved to a structure

MNDR:
- Move transport string generation to own function, which can be overloaded or sniffed

MNDR:
- move connection establishment code to own command - COM_HANDSHAKE

MNDR:
- convert the API of MYSQLND_NET to MYSQLND_STRING

MNDR:
- decouple the commands from the connection. CONN ist passed now only in 1 case

MNDR:
- clean up some things

MNDR:
- move COM_INIT_DE result handling to the command

MNDR:
- remove COM_FIELD_LIST