Fixes for OSX 10.8 & Intel compiler.

It doesn't generate a symbol for the destructor of the *FileLoader
interfaces unless explicitly defined. All other platforms, including
OS X 10.6, don't show this problem.
Refs #7263

Code/Mantid/Framework/API/inc/MantidAPI/IFileLoader.h

@@ -36,6 +36,8 @@ namespace Mantid
     class MANTID_API_DLL IFileLoader : public Algorithm
     {
     public:
+      /// Virtual destructor (required by linker on some versions of OS X/Intel compiler)
+      virtual ~IFileLoader() {}
       /// Returns a confidence value that this algorithm can load a file
       virtual int confidence(Kernel::FileDescriptor & descriptor) const = 0;
     };

Code/Mantid/Framework/API/inc/MantidAPI/IHDFFileLoader.h

@@ -36,6 +36,8 @@ namespace Mantid
     class DLLExport IHDFFileLoader : public API::Algorithm
     {
     public:
+      /// Virtual destructor (required by linker on some versions of OS X/Intel compiler)
+      virtual ~IHDFFileLoader() {}
       /// Returns a confidence value that this algorithm can load a file
       virtual int confidence(Kernel::HDFDescriptor & descriptor) const = 0;
     };