Fix build in C++11 mode

Make sure "_"SK_SIZE_T_SPECIFIER isn't interpreted as a C++11 literal by
adding a space

Change-Id: I9c1c30f733124812b916ac1ae113ffceab65bad0
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@linaro.org>
Merge "Fix build in C++11 mode"