Wintermute has released devkitPPC r28 and libOGC v1.8.15 for the Wii U, heres more details:
The binaries for devkitPPC release 28 and libogc 1.8.15 are now available. As usual the windows binaries are available through the Automated Installer/Updater, for other platforms check the devkitPPC getting started page on the wiki.
devkitPPC release 28
updated to gcc 6.2.0.
updated binutils to 2.27.
updated newlib to 2.0.0.
updated gdb to 7.11.
libogc 1.8.15
Enable QOS guaranteed devices support in lwbt.
Improve Wii MotionPlus detection and initialization.
Fix 3rd party classic controllers, add wii u pro controller support.
Fix gamecube BBA support.
Added option for retries to ifconfig.
Various fixes to compile with latest gcc.
The Wii and Gamecube examples have also been updated to compile with devkitPPC r28/libogc 1.8.15