proftpd : updated to v 1.3.8c ; more databases ; config changes

[BjarneDMat]

* update to version 1.3.8c
* sysconfir & localstatedir into own subdirs
* mysql8 & postgresql17 variants added
  addresses : https://trac.macports.org/ticket/43431
* modified patch to fix original m4 file
  reported : https://github.com/proftpd/proftpd/issues/1878
* autoconf : yes ; to re-create configure files due to patch
* DRY changes

Changes to be committed:
        modified:   net/proftpd/Portfile
        modified:   net/proftpd/files/dynamic_lookup-11.patch
        new file:   net/proftpd/files/-Wimplicit-function-declaration
                to-do file
                https://github.com/proftpd/proftpd/issues/1879

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 14.7.3 23H417 x86_64
Xcode 16.2 16C5032a

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?