Fix typos in manpages, catched by Lintian

docs/libssh2_knownhost_writeline.3

@@ -35,7 +35,7 @@ and 0 indicates success.
 
 If the provided buffer is deemed too small to fit the data libssh2 wants to
 store in it, LIBSSH2_ERROR_BUFFER_TOO_SMALL will be returned. The application
-is then adviced to call the function again with a larger buffer. The
+is then advised to call the function again with a larger buffer. The
 \fIoutlen\fP size will then hold the requested size.
 .SH AVAILABILITY
 Added in libssh2 1.2

docs/libssh2_sftp_fstat_ex.3

@@ -60,7 +60,7 @@ You will find a full set of defines and macros to identify flags and
 permissions on the \fBlibssh2_sftp.h\fP header file, but some of the
 most common ones are:
 
-To check for specific user permissons, the set of defines are in the
+To check for specific user permissions, the set of defines are in the
 pattern LIBSSH2_SFTP_S_I<action><who> where <action> is R, W or X for
 read, write and excutable and <who> is USR, GRP and OTH for user,
 group and other. So, you check for a user readable file, use the bit

docs/libssh2_sftp_last_error.3

@@ -17,7 +17,7 @@ libssh2_sftp_last_error(LIBSSH2_SFTP *sftp);
 Returns the last error code produced by the SFTP layer. Note that this only
 returns a sensible error code if libssh2 returned LIBSSH2_ERROR_SFTP_PROTOCOL
 in a previous call. Using \fBlibssh2_sftp_last_error(3)\fP without a
-preceeding SFTP protocol error, it will return an unspecified value.
+preceding SFTP protocol error, it will return an unspecified value.
 
 .SH RETURN VALUE
 Current error code state of the SFTP instance.

docs/libssh2_sftp_stat_ex.3

@@ -25,7 +25,7 @@ libssh2_sftp_setstat(LIBSSH2_SFTP *sftp, const char *path, LIBSSH2_SFTP_ATTRIBUT
 
 \fIpath\fP - Remote filesystem object to stat/lstat/setstat.
 
-\fIpath_len\fP - Lenght of the name of the remote filesystem object 
+\fIpath_len\fP - Length of the name of the remote filesystem object 
 to stat/lstat/setstat.
 
 \fIstat_type\fP - One of the three constants specifying the type of