man: fix double spaces and dash escaping

- `-  ` -> `- `
- `.  ` -> `. `
- `\- ` -> `- `
- `-1` -> `\-1`
- fold long lines along the way

This makes the minus sign come out as a Unicode minus sign
(0x2212), and title separator dashes as Unicode hyphen (0x2010),
with `groff -Tutf8` v1.23.0.

Ref: https://lwn.net/Articles/947941/

Closes #1210

docs/libssh2_banner_set.3

@@ -22,7 +22,8 @@ instead!
 Set the banner that will be sent to the remote host when the SSH session is
 started with
 .BR libssh2_session_handshake(3)
-  This is optional; a banner corresponding to the protocol and libssh2 version will be sent by default.
+This is optional; a banner corresponding to the protocol and libssh2 version
+will be sent by default.
 .SH RETURN VALUE
 Return 0 on success or negative on failure. It returns
 LIBSSH2_ERROR_EAGAIN when it would otherwise block. While

docs/libssh2_channel_forward_cancel.3

@@ -14,7 +14,8 @@ libssh2_channel_forward_cancel(LIBSSH2_LISTENER *listener);
 \fIlistener\fP - Forwarding listener instance as returned by
 .BR libssh2_channel_forward_listen_ex(3)
 
-Instruct the remote host to stop listening for new connections on a previously requested host/port.
+Instruct the remote host to stop listening for new connections on a previously
+requested host/port.
 .SH RETURN VALUE
 Return 0 on success or negative on failure. It returns
 LIBSSH2_ERROR_EAGAIN when it would otherwise block. While

docs/libssh2_free.3

@@ -12,8 +12,8 @@ libssh2_free(LIBSSH2_SESSION *session, void *ptr);
 .fi
 .SH DESCRIPTION
 Deallocate memory allocated by earlier call to libssh2 functions. It
-uses the memory allocation callbacks provided by the application, if
-any.  Otherwise, this will call free().
+uses the memory allocation callbacks provided by the application, if any.
+Otherwise, this will call free().
 
 This function is mostly useful under Windows when libssh2 is linked to
 one run-time library and the application to another.

docs/libssh2_session_callback_set.3

@@ -51,7 +51,7 @@ send, \fBlength\fP is the size of the data, \fBflags\fP is the flags that
 would have been used to a \fIsend()\fP call and \fBabstract\fP is a pointer
 to the abstract pointer set in the \fIlibssh2_session_init_ex(3)\fP call.
 
-The callback returns the number of bytes sent, or -1 for error. The special
+The callback returns the number of bytes sent, or \-1 for error. The special
 return code \fB-EAGAIN\fP can be returned to signal that the send was aborted
 to prevent getting blocked and it needs to be called again.
 .IP LIBSSH2_CALLBACK_RECV
@@ -70,7 +70,7 @@ data into, \fBlength\fP is the size of the buffer, \fBflags\fP is the flags
 that would have been used to a \fIrecv()\fP call and \fBabstract\fP is a pointer
 to the abstract pointer set in the \fIlibssh2_session_init_ex(3)\fP call.
 
-The callback returns the number of bytes read, or -1 for error. The special
+The callback returns the number of bytes read, or \-1 for error. The special
 return code \fB-EAGAIN\fP can be returned to signal that the read was aborted
 to prevent getting blocked and it needs to be called again.
 .IP LIBSSH2_CALLBACK_AUTHAGENT

docs/libssh2_session_get_blocking.3

@@ -2,7 +2,7 @@
 .\" SPDX-License-Identifier: BSD-3-Clause
 .TH libssh2_session_get_blocking 3 "1 Jun 2007" "libssh2 0.15" "libssh2"
 .SH NAME
-libssh2_session_get_blocking \- evaluate blocking mode on session
+libssh2_session_get_blocking - evaluate blocking mode on session
 .SH SYNOPSIS
 .nf
 #include <libssh2.h>