unwind: unify some more macros
unwind: unify some more macros

The macros were defined identically across both cases.  Unify the definitions to
have a single definition for _LIBUWNIND_{HIDDEN,EXPORT} and _LIBUNWIND_LOG.
NFC.

git-svn-id: 62ef012455b6b8fcec9c41ca270ebf409aae1006@267169 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libunwind,llvm-mirror/libunwind,llvm-mirror/libunwind