Android: Fix for compilation error in clucene.

Android only provide stubs for wcstoll(3) and wctomb(3), to solve this
wcstoll(3) is replace by an internal equvialent, and wctomb(3) by
wcrtomb(3).

Change-Id: Ic30e5a809c2f6ab30b4e52883d3aae3ecc036194
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>