Remove PAM dependency code.
The libpam dependency was brought 3.5 years due to c-client.  As of today,
there's no need neither in HHVM or c-client to link against libpam.
HHVM itself does not depend on boost_regex.
Only third-party/folly depends on libboost_regex, but HHVM has a
dependency that causes a bogus linkage in the final binary.

Sync with Debian patch 09_remove_boost_regex_hhvm.patch from 2.4.1-1.
Disable bogus code for finding and linking against ncurses.
For some very old reason lost in the dawn of time, HHVM imported the
CMake file of Readline from KDE, which had an ncurses dependency. Remove it
from everywhere.

Sync with Debian patch 08_disable_libncurses.patch from 2.4.1-1.
Merge pull request #2085 from Jo-Con-El/debian-10_remove_libpam

Remove PAM dependency code.
Merge pull request #2086 from Jo-Con-El/debian-09_remove_boost_regex_hhvm

HHVM itself does not depend on boost_regex.
Merge pull request #2087 from Jo-Con-El/debian-08_disable_libncurses

Disable bogus code for finding and linking against ncurses.