Clean up some of the Android icu4c hacks.

We don't need the ustr_wcs.cpp hack: bionic's stdlib.h contains
the same #define.

We don't need the digitlst.cpp hack: we can just modify the makefile
so we can use stlport.

We don't need most of the putil.cpp hacks, and the two we do need can
be done in the makefile.

Change-Id: If67d307688347f9c04febed3ecfe6f36b7effc9d
5 files changed