Change #264197

Comments

configure: tidy up comments
- convert `#` comments to `dnl`, except copyright headers, and inline
  comments in `curl-complilers.m4`.
- drop empty comments.
- drop line-ending `dnl` markers. (except `zz40-xc-ovr.m4` where it's
  used to produce a comment in `configure`.)
- replace `dnl` line with C comment in `AC_CHECK_HEADERS()`.

Verified to produce the same `configure` script except empty lines,
`#` comments, and C comments, with autoreconf 2.72.

Cherry-picked from #21000

Closes #21246

Changed files

• acinclude.m4
• configure.ac
• docs/libcurl/libcurl.m4
• m4/curl-amissl.m4
• m4/curl-compilers.m4
• m4/curl-confopts.m4
• m4/curl-functions.m4
• m4/curl-gnutls.m4
• m4/curl-openssl.m4
• m4/curl-override.m4
• m4/curl-reentrant.m4
• m4/curl-rustls.m4
• m4/curl-schannel.m4
• m4/xc-am-iface.m4
• m4/xc-cc-check.m4
• m4/xc-lt-iface.m4
• m4/xc-val-flgs.m4
• m4/zz40-xc-ovr.m4
• m4/zz50-xc-ovr.m4