libcrypt is no longer part of glibc, so it might not be available.

Signed-off-by: Piotr Sikora <piotr@aviatrix.com>

The build location of the resulting libatomic_ops.a was changed in v7.4.0
after converting libatomic_ops to use libtool.  The fix is to use library
from the install path, this allows building with both old and new versions.

Initially reported here:
https://mailman.nginx.org/pipermail/nginx/2018-April/056054.html

Added ngx_openssl_cache_module, which indexes a type-aware object cache.
It maps an id to a unique instance, and provides references to it, which
are dropped when the cycle's pool is destroyed.

The cache will be used in subsequent patches.

Based on previous work by Mini Hawthorne.

Using "long *" instead of "AO_t *" leads either to -Wincompatible-pointer-types
or -Wpointer-sign warnings, depending on whether long and size_t are compatible
types (e.g., ILP32 versus LP64 data models).  Notably, -Wpointer-sign warnings
are enabled by default in Clang only, and -Wincompatible-pointer-types is an
error starting from GCC 14.

Signed-off-by: Edgar Bonet <bonet@grenoble.cnrs.fr>

Signed-off-by: Piotr Sikora <piotr@aviatrix.com>

Signed-off-by: Piotr Sikora <piotr@aviatrix.com>

Signed-off-by: Piotr Sikora <piotr@aviatrix.com>

Based on a patch by Piotr Sikora.