[ARC] Make char unsigned by default

[apolyakov]

Summary

This patch specifies 'char' default sign on ARC.

[tatyana-krasnukha]

Good to me, if no one is confused about absent general support of ARC target. Please, add @clayborg to reviewers.

lldb/trunk/source/Utility/ArchSpec.cpp

bool ArchSpec::CharIsSignedByDefault() const {
 
   case llvm::Triple::ppc:
   case llvm::Triple::ppc64:
     return m_triple.isOSDarwin();
 
   case llvm::Triple::ppc64le:
   case llvm::Triple::systemz:
   case llvm::Triple::xcore:
+  case llvm::Triple::arc:
     return false;
   }
 }
 
 lldb::ByteOrder ArchSpec::GetByteOrder() const {
   if (m_byte_order == eByteOrderInvalid)
     return GetDefaultEndian();
   return m_byte_order;