[PATCH] demangle undefined symbol names in error message

[Rui Ueyama]

LGTM with nits

================
Comment at: include/lld/Core/LinkingContext.h:274
@@ +273,3 @@
+  /// Formats symbol name for use in error messages.
+  virtual std::string demangleSymbol(StringRef symbolName) const {
+    return symbolName;
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I'd name demangle rather than demangleSymbol because it's shorter and yet conveys enough information.

================
Comment at: include/lld/ReaderWriter/MachOLinkingContext.h:100
@@ -97,1 +99,3 @@
   void setKeepPrivateExterns(bool v) { _keepPrivateExterns = v; }
+  bool demangle() const { return _demangle; }
+  void setDemangle(bool d) { _demangle = d; }
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And rename doDemangle, enableDemangle or something like that.

http://reviews.llvm.org/D5549