A group of related fixes to fix the CMake build for Visual Studio (2015). Tested against trunk and 2.4.20.

0001: On my machine, the current implementation isn't able to correctly discover APR features (like APU_HAVE_CRYPTO). Setting CMAKE_REQUIRED_INCLUDES to APR's include directory seems to fix this problem.

0002: The current implementation assumes .lib and related files will always be placed directly inside the build root. But Visual Studio is a multi-configuration generator, which means that output files may be placed in a per-configuration subdirectory. To fix this, use CMake generator expressions instead of hardcoding the paths to these files.

0003: Calls to Perl during installation did not quote the file path arguments, so the installation would fail if the target path contained spaces (e.g. "Program Files"). Quote all of these paths.