vssh: drop support for wolfSSH

The implementation was incomplete and lesser than the other backends. No
one ever reported a bug or requested enhancements for this, indicating
that this backend was never used.

Closes #18700

docs/INSTALL-CMAKE.md

@@ -363,7 +363,6 @@ Details via CMake
 - `CURL_USE_PKGCONFIG`:                     Enable `pkg-config` to detect dependencies. Default: `ON` for Unix (except Android, Apple devices), vcpkg, MinGW if not cross-compiling.
 - `CURL_USE_RUSTLS`:                        Enable Rustls for SSL/TLS. Default: `OFF`
 - `CURL_USE_SCHANNEL`:                      Enable Windows native SSL/TLS (Schannel). Default: `OFF`
-- `CURL_USE_WOLFSSH`:                       Use wolfSSH. Default: `OFF`
 - `CURL_USE_WOLFSSL`:                       Enable wolfSSL for SSL/TLS. Default: `OFF`
 - `CURL_ZLIB`:                              Use zlib (`ON`, `OFF` or `AUTO`). Default: `AUTO`
 - `CURL_ZSTD`:                              Use zstd (`ON`, `OFF` or `AUTO`). Default: `AUTO`
@@ -447,8 +446,6 @@ Details via CMake
 - `RUSTLS_INCLUDE_DIR`:                     The Rustls include directory.
 - `RUSTLS_LIBRARY`:                         Path to `rustls` library.
 - `WATT_ROOT`:                              Set this variable to the root installation of Watt-32.
-- `WOLFSSH_INCLUDE_DIR`:                    The wolfSSH include directory.
-- `WOLFSSH_LIBRARY`:                        Path to `wolfssh` library.
 - `WOLFSSL_INCLUDE_DIR`:                    The wolfSSL include directory.
 - `WOLFSSL_LIBRARY`:                        Path to `wolfssl` library.
 - `ZSTD_INCLUDE_DIR`:                       The zstd include directory.

docs/KNOWN_BUGS

@@ -60,11 +60,9 @@ problems may have been fixed or changed somewhat since this was written.
 
  9. SFTP and SCP
  9.1 SFTP does not do CURLOPT_POSTQUOTE correct
- 9.2 wolfssh: publickey auth does not work
  9.3 Remote recursive folder creation with SFTP
  9.4 libssh blocking and infinite loop problem
  9.5 Cygwin: "WARNING: UNPROTECTED PRIVATE KEY FILE!"
- 9.6 wolfssh: all tests fail
 
  10. Connection
  10.1 --interface with link-scoped IPv6 address
@@ -400,14 +398,6 @@ problems may have been fixed or changed somewhat since this was written.
  report but it cannot be accepted as-is. See
  https://curl.se/bug/view.cgi?id=748
 
-9.2 wolfssh: publickey auth does not work
-
- When building curl to use the wolfSSH backend for SFTP, the publickey
- authentication does not work. This is simply functionality not written for curl
- yet, the necessary API for make this work is provided by wolfSSH.
-
- See https://github.com/curl/curl/issues/4820
-
 9.3 Remote recursive folder creation with SFTP
 
  On this servers, the curl fails to create directories on the remote server
@@ -429,12 +419,6 @@ problems may have been fixed or changed somewhat since this was written.
 
  https://github.com/curl/curl/issues/11244
 
-9.6 wolfssh: all tests fail
-
- Something fundamental stops them all from working properly.
-
- https://github.com/curl/curl/issues/16794
-
 10. Connection
 
 10.1 --interface with link-scoped IPv6 address

docs/tests/FILEFORMAT.md

@@ -513,7 +513,6 @@ Features testable here are:
 - `wakeup`
 - `win32`
 - `WinIDN`
-- `wolfssh`
 - `wolfssl`
 - `xattr`
 - `zstd`