Package apt: Information

- e2k: Fixed the compilation of dependent packages with unchanged flags.
  (Restored the e2k source code adaptations; simply removing them in
  0.5.15lorg2-alt93 was wrong due to possible ABI or API breakage.)

- Build for p10: with some fixes (corrupt downloads, IPv6 literals, etc.),
  and with the new feature of HTTPS over an HTTP proxy,
  but with the experimental columnar output turned off.

- Added support for HTTPS connections through an HTTP proxy (ALT#38543).
  (Backported from Debian 1.5_alpha4~9.) (To come next: through HTTPS proxy.)
  Applicable configuration is the same as for HTTP.
- Fixes:
  + OVE-20250602-0002 Not using HTTPS from behind a proxy opens doors for
  exploiting APT's bugs.
  When using APT from behind a proxy, impossibility to use a trusted
  connection to the trusted vendor's HTTPS server may open doors for an
  attack on APT's http method that would make APT misbehave and execute
  arbitrary code (in a package) prepared by an attacker who controls one
  of the connection nodes, e.g., by exploiting any bug in APT that would
  lead to misinterpretation of internal responses from the http method,
  which--among other things--has the power to fake computed checksums.