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
diff --git a/src/locale.cpp b/src/locale.cpp
index 148fe42..e626528 100644
--- a/src/locale.cpp
+++ b/src/locale.cpp
@@ -1038,7 +1038,7 @@
 #elif defined(_AIX)
     return (const unsigned int *)__lc_ctype_ptr->obj->mask;
 #elif defined(__ANDROID__)
-    return _ctype_ + 1;
+    return reinterpret_cast<const unsigned char*>(_ctype_) + 1;
 #else
     // Platform not supported: abort so the person doing the port knows what to
     // fix