- Change the path of the Sys folder to the executable's location
- Add LINUX_LOCAL_DEV flag to use relocatable version on Linux
- Add CMake definition for relocatable build

Currently only works on unix, but can be extended to other systems. Can
also be extended to do wiimotes.

Searches the Pipes folder for readable named pipes and creates a dolphin
input device out of them. Send controller inputs to the game by writing
to the file. Commands are described in Pipes.h.

Fixes the regression from a225426 and clarifies a related comment.

Eventually, netplay will be able to use the host's NAND, but this could
still be useful in some cases; for TAS it definitely makes sense to have
a way to avoid using any preexisting NAND.

In terms of implementation: remove D_WIIUSER_IDX, which was just WIIROOT
+ "/", as well as some other indices which are pointless to have as
separate variables rather than just using the actual path (fixed, since
they're actual Wii NAND paths) at the call site.  Then split off
D_SESSION_WIIROOT_IDX, which can point to the dummy NAND directory, from
D_WIIROOT_IDX, which always points to the "real" one the user
configured.

- FileSearch is now just one function, and it converts the original glob
  into a regex on all platforms rather than relying on native Windows
  pattern matching on there and a complete hack elsewhere.  It now
  supports recursion out of the box rather than manually expanding
  into a full list of directories in multiple call sites.

  - This adds a GCC >= 4.9 dependency due to older versions having
  outright broken <regex>.  MSVC is fine with it.

- ScanDirectoryTree returns the parent entry rather than filling parts
  of it in via reference.  The count is now stored in the entry like it
  was for subdirectories.

- .glsl file search is now done with DoFileSearch.

- IOCTLV_READ_DIR now uses ScanDirectoryTree directly and sorts the
  results after replacements for better determinism.