Make Android's ctype_base::mask unsigned.

Keeping the regex code sane is much easier if we match the other
platforms and use an unsigned mask.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@214442 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 3ab406107dcdbe10ec2b3f2f8ce37129d132b71a)

Change-Id: If15df5f68783a23cbfc60075355f8481d60c11db
2 files changed