Enclose code in namespace instead of 'using namespace' to resolve conflict on Windows with MSXML. Fixes issue #37.

tinyxml2.cpp

@@ -30,7 +30,6 @@ distribution.
 #   include <cstddef>
 #endif
 
-using namespace tinyxml2;
 using namespace std;
 
 static const char LINE_FEED				= (char)0x0a;			// all line endings are normalized to LF
@@ -64,6 +63,9 @@ static const unsigned char TIXML_UTF_LEAD_2 = 0xbfU;
         }										\
     }
 
+namespace tinyxml2
+{
+
 struct Entity {
     const char* pattern;
     int length;
@@ -2084,3 +2086,5 @@ bool XMLPrinter::Visit( const XMLUnknown& unknown )
     PushUnknown( unknown.Value() );
     return true;
 }
+
+}