stlport: Fix incompatibility with clang++ (used by llvm) in ISO C++11…

… mode

clang++ has a strange idea about wchar_t

Change-Id: I9f73e88cc06c35e988b33576ea235046ea51d546
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>