Replace with `ssh2_deb()`.
Also:
- adjust checksrc options to verify.
- checksrc-all.pl: fix an issue preventing picking up `tests/.checksrc`.
Follow-up to c090b696c6#1556
Follow-up to af1e591eee#796Closes#1997
- configure: use `dnl`-style comments consistently (where possible).
- configure: drop stray spaces.
- wincng: replace Windows-specific type in `memcpy()` casts.
- drop FIXME added incorrectly in a recent commit.
Follow-up to ecf39b3634#1984
Follow-up to ff50682c23#1679
- replace more synonyms with 'null-terminated'.
- unfold strings, comments and code lines.
- reflow lines, fix indent.
Closes#1995
- fix typos in comments and documentation.
- fix references to non-existing functions in comments.
- libssh2_session_free: fix see-also reference on man page.
- libssh2_scp_recv2: fix typo in prototype on man page.
- man2help: use increment operator.
- badwords: extend with new words and an exclusion.
- userauth: unfold string.
- clang-format and manual formatting.
Closes#1988
Checker script and wordlist comes from curl.
Also:
- checksrc.pl: sync up with curl.
- unfold an IETF URL.
- update all IETF URLs where missing.
Closes#1959
Keep `lib-link.m4`, rename to `libssh2-link.m4`, namespace its content
to `LIBSSH2_`. Also copy 3 lower-level functions from another `.m4`.
Drop using vendored `AC_LIB_PROG_LD`, which served the purpose of
detecting `LD` and `with_gnu_ld`.
To reduce amount of old, complex vendored code and also to avoid
autoreconf auto-updating these in-repo files locally.
Follow-up to 0443145a75#1920
Follow-up to bcc9292aab#1921Closes#1916
To reduce differences with curl.
Also:
- add most scripts to the source distro tarball. Some were referenced
by build scripts (e.g. `checksrc`).
Closes#1870
