Update Mac apr_suite package, introducing libapr-1.0.3.7.dylib and
libaprutil-1.0.3.8.dylib. We want to use dynamic APR libraries, but
libllcommon.dylib isn't allowed to depend on .so libraries: must be .dylibs
themselves.
Tweak APR.cmake to reference the aforementioned .dylibs when on Mac with
LLCOMMON_LINK_SHARED set. Eliminate some redundancy in Windows section.
For .dylibs, RunBuildTest.cmake must set DYLD_LIBRARY_PATH: LD_LIBRARY_PATH
only affects search for .so files.

PENDING:
CMake dependencies broken? With LLCOMMON_LINK_SHARED on, it seems we need to
build libllcommon.dylib explicitly before full build can succeed.
This snapshot does NOT yet copy the llcommon, apr or aprutil dylibs into the
app bundle.