Simplified _libssh2_check_length (#350)
Simplified _libssh2_check_length (#350)

* Simplified _libssh2_check_length

misc.c : _libssh2_check_length()

Removed cast and improved bounds checking and format.

Credit : Yuriy M. Kaminskiy

libssh2/libssh2,libssh2/libssh2,libssh2/libssh2,libssh2/libssh2