Update perlang-install to detect tls1.2 for curl 7.73+

[perlun]

As can be seen in the perlang-install sceencast at https://perlang.org/download/, certain versions of cURL fails in terms of the TLS 1.2 detection. This is the error we emit in these cases:

Warning: Not enforcing strong cipher suites for TLS, this is potentially less secure
Warning: Not enforcing TLS v1.2, this is potentially less secure                                                                                                                 

The root cause for this is that the curl --help syntax has changed in recent versions (and ideally, parsing the curl --help output isn't a particularly great way anyway, but there's probably not much we can do about that). This commit, originally done by @apnorton in rust-lang/rustup#2604 (thanks!) fixes the issue. Given that perlang-install is essentially a fork of rustup-init.sh, the patch applied cleanly after merely editing the file name.

(After importing the commit, I did change the author of the commit to myself, since it would be a bit misleading to just copy commits from another author in another repo into this repo without their consent; it just looked weird that way.)

Original commit message

(from rust-lang/rustup@01fd3a1)

This fixes rust-lang/rustup#2603. In curl 7.73.0, the help format was
changed so as to only show a summary when calling curl --help, while
the old menu can be accessed as curl --help all. This change updates
the check_help_for function to detect if the command being checked
contains the curl 7.73.0+ language indicating the use of --help all.

If this language is present, check_help_for will insert the all
category after the --help flag, allowing the query to work. If the
language is not present, then it will insert an empty string following
the --help flag, maintaining the same behavior with pre-7.73 versions
of curl.