After reinstatement of DSO support in APR/APR-util, revert r1837437,

After reinstatement of DSO support in APR/APR-util, revert r1837437,
r1837435, r1834553, r1833598, r1833452, r1833383, r1833368.

Undoes the following:

mod_ssl: OpenSSL now initializes fully through APR, use that.

mod_ssl: build with LibreSSL.

LibreSSL seems to be openssl-1.1 API compatible only in version 2.8 (master).
So use that for MODSSL_USE_OPENSSL_PRE_1_1_API instead of 2.7, the two 2.7
compatibility-exceptions are handled explicitely but overall it's simpler.

Regarding CRYPTO_malloc_init vs OPENSSL_malloc_init, libreSSL uses none, the
former used to be a no-op but depends is LIBRESSL_INTERNAL in latest versions,
while the latter has never been (and will never be) defined. So don't call any
with LibreSSL.

Follow up to r1833368: share openssl between modules.

Both libapr[-util], the core PRNG, mod_ssl, mod_crypto and mod_session_crypto
can use the same crypto library (e.g. openssl), use the new APR crypto loading
API so that they can work together and initialize/terminate the lib either once
for all or on demand and reusable by the others.

Follow up to r1833368: apr_crypto_prng_after_fork() now used a PID.

Make use of the new apr_crypto_rng API if available.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1861947 13f79535-47bb-0310-9956-ffa450edef68