Distros like Debian/Ubuntu use architecture-specific directory structures
(like /usr/lib/x86_64-linux-gnu) which we cannot hardcode/guess, so we
really need to search the default paths.
Added missing CMake defines for SVN_CLIENT.
Don't detect libsvn without APR.
When installed, enable libsvn support by default (same as for automake).
When enabled, provide libsvn include dir to libtsync.
gitignore temporary CMake files