[Common] Abstract out the decode5A3Image and decodeCI8Image functions in BannerLoaderGC, BannerLoaderWii, and GCMemcard into ColorUtil.cpp. Makes for less copied code and remains functionally the same.
Warning fixes:

- Don't use %lu for size_t; they're different on Linux x86.

- has_warned_about_drivers is only used on win32, so only declare it
  there to avoid a unused variable warning.
[Android] Simplify call for getting the WindowManager instance within EmulationActivity.
[Android] Simplify a string retrieval in FolderBrowserAdapter.

Also remove an unnecessary import from EmulationActivity.java. This should have been removed in the previous commit.
[Android] Simplify LayoutInflater retrieval within GameListAdapter, FolderBrowserAdapter, and SideMenuAdapter.

Also added Javadoc to SideMenuAdapter. Gave the context variables a full spelling as well.
[Android] Make sure to change the title accordingly when coming back from the folder browser.
[ARM] Disable subfic, it prevents Wind Waker from booting into a save game.
ChooseMemcardPath bugfix: check for a directory separator before converting an absolute path to a relative path.

if the exe directory and the save directory had the same prefix, .../dolphin emulator/... and .../dolphin/... the path would previously have been incorrectly changed