BuildSystem: Check for alternate openssl packages

OpenSSL is one of those packages that often have alternatives
with later versions.  For instance, CentOS/EL 7 has an
openssl package at version 1.0.2 but there's an openssl11
package from the epel repository that has 1.1.1.  This gets
installed to /usr/include/openssl11 and /usr/lib64/openssl11.
Unfortunately, the existing --with-ssl and --with-crypto
./configure options expect to point to a source tree and
don't work in this situation.  Also unfortunately, the
checks in ./configure don't use pkg-config.

In order to make this work with the existing situation, you'd
have to run...
./configure --with-ssl=/usr/lib64/openssl11 \
    --with-crypto=/usr/lib64/openssl11 \
    CFLAGS=-I/usr/include/openssl11

BUT...  those options don't get passed down to bundled pjproject
so when you run make, you have to include the CFLAGS again
which is a big pain.

Oh...  To make matters worse, although you can specify
PJPROJECT_CONFIGURE_OPTS on the ./configure command line,
they don't get saved so if you do a make clean, which will
force a re-configure of bundled pjproject, those options
don't get used.

So...

* In configure.ac... Since pkg-config is installed by install_prereq
  anyway, we now use it to check for the system openssl >= 1.1.0.
  If that works, great.  If not, we check for the openssl11
  package. If that works, great.  If not, we fall back to just
  checking for any openssl.  If pkg-config isn't installed for some
  reason, or --with-ssl=<dir> or --with-crypto=<dir> were specified
  on the ./configure command line, we fall back to the existing
  logic that uses AST_EXT_LIB_CHECK().

* The whole OpenSSL check process has been moved up before
  THIRD_PARTY_CONFIGURE(), which does the initial pjproject
  bundled configure, is run.  This way the results of the above
  checks, which may result in new include or library directories,
  is included.

* Although not strictly needed for openssl, We now save the value of
  PJPROJECT_CONFIGURE_OPTS in the makeopts file so it can be used
  again if a re-configure is triggered.

ASTERISK-29693

Change-Id: I341ab7603e6b156aa15a66f43675ac5029d5fbde