Add support for APU_HAVE_CRYPTO+APU_HAVE_OPENSSL.

(Fully-qualifying the include file paths was implemented as part
of specifying the include directories for apr_crypto_openssl-2;
relative include paths don't work with SET_TARGET_PROPERTIES(
... INCLUDE_DIRECTORIES ... ) )

Update notes on what needs to be done:
. OpenSSL flavor of APU_HAVE_CRYPTO is done as of this commit
. COMMONCRYPTO is OS X/iOS, so that isn't applicable to Windows
. APU_DSO_MODULE_BUILD is the style we have; static module builds
  is what is missing



git-svn-id: https://svn.apache.org/repos/asf/apr/apr/trunk@1518029 13f79535-47bb-0310-9956-ffa450edef68