added test case 27 for testing error handlers
added PHPIREDIS_ERROR_CONNECTION and PHPIREDIS_ERROR_PROTOCOL constants, added phpiredis_set_error_handler() function with copied code
added error callback to _phpiredis_connection struct
use a proper callback in the test
expanded test, checks for function present and does a faulty operation
proper function declaration for free_error_handler(), use the right macros for accessing arguments
removed superfluous returns
removed TODO from phpiredis_set_error_handler()
call error handler if it is set
expanded test to check the *_bs functions as well
extend test with checks for some error conditions
tabs to spaces
refactored error handler calling code into separate function
free error callback when destroying the connection
need to include the thread safety parameters
removed merge error marks....... again
modified signature of handle_error_callback() to accept a string instead of an redisReply
call error handler for connection errors also
refactored callback calling again to reduce some duplicate code
set an empty error handler in test 008