Check for NULL channel pointers
legacy: Fixed the symbol export.
legacy: Added missing channel_write_stderr.
messages: Added missing config.h include.
build: Set version to 0.5.90.
doc: Improved documentation for server options.
doc: Improve the doc of ssh_bind_set_callbacks.
doc: Fixed typos in messaging introduction.
doc: Added missing doc for common message function.
doc: More doc for messaging functions.
messages: Make returned strings const.
example: Use const in auth_password from samplesshd.
Added a IP address test
Implement ssh_blocking_flush()

Based on code from Jan Willamowius
Fix the ssh_message_retrieve problem by anihilation
doc: Extremly important README update!
Change session state after receiving a Disconnect
Fixed doc of ssh_userauth_list()
sftp: Fixed double-free in sftp_unlink().
cmake: Fixed a typo.