Place fixed width fundamental types into the adios namespace

This allows us to both drop the namespace prefix when using them in
implementation and guarantee that we don't use versions of the types
that get re-defined elsewhere.

In order to provide the least ammount of disruption this doesn't include
any sweeping search and replace changes.  However, it is recommended
moving forward that these types be used internally when fixed width
sizes are expected.  This will allow the transition to happen gradually
through attrition and minimize conflicts.

include/ADIOSTypes.h

@@ -11,6 +11,10 @@
 #ifndef ADIOS_TYPES_H_
 #define ADIOS_TYPES_H_
 
+#include <complex>
+#include <cstddef>
+#include <cstdint>
+
 namespace adios
 {
 
@@ -37,6 +41,26 @@ enum class IOMode
     COLLECTIVE = 1
 };
 
-} // end namespace
+// Alias the fixed sized typed into the adios namespace to make sure we're
+// always using the right ones.
+using std::size_t;
+
+using std::int8_t;
+using std::uint8_t;
+using std::int16_t;
+using std::uint16_t;
+using std::int32_t;
+using std::uint32_t;
+using std::int64_t;
+using std::uint64_t;
+
+// Not sure if we're really use these ones but we'll round it out for
+// completion
+using real32_t = float;
+using real64_t = double;
+using complex32_t = std::complex<real32_t>;
+using complex64_t = std::complex<real64_t>;
+
+} // end namespace adios
 
 #endif /* ADIOS_TYPES_H_ */