man: fixups

- add missing `.fi` tags.
- fix misplaced `.nf` tags.
- add `.nf`/`.fi` tags `SYNOPSIS` where missing.
- fix missing/wrong function name from `SH NAME`.
- fix wrong function name in `TH`.
- keep return values in a separate line.
- indent.
- fold long lines.
- deleted `libssh2_channel_direct_streamlocal()`, there is no such function.
- add missing types.
- add missing headers.

Closes #949

docs/libssh2_knownhost_add.3

@@ -1,4 +1,4 @@
-
+.\"
 .\" Copyright (c) 2009, 2010 by Daniel Stenberg
 .\"
 .TH libssh2_knownhost_add 3 "28 May 2009" "libssh2 1.2" "libssh2 manual"
@@ -8,11 +8,13 @@ libssh2_knownhost_add - add a known host
 .nf
 #include <libssh2.h>
 
-int libssh2_knownhost_add(LIBSSH2_KNOWNHOSTS *hosts,
-                          char *host, char *salt,
-                          char *key, size_t keylen,
-                          int typemask,
-                          struct libssh2_knownhost **store);
+int
+libssh2_knownhost_add(LIBSSH2_KNOWNHOSTS *hosts,
+                      char *host, char *salt,
+                      char *key, size_t keylen,
+                      int typemask,
+                      struct libssh2_knownhost **store);
+.fi
 .SH DESCRIPTION
 We discourage use of this function as of libssh2 1.2.5. Instead we strongly
 urge users to use \fIlibssh2_knownhost_addc(3)\fP instead, which as a more