Fix Windows warnings and build

Author: silvakid

cppconn/connection.h

@@ -156,7 +156,7 @@ enum ssl_mode
   SSL_MODE_VERIFY_CA, SSL_MODE_VERIFY_IDENTITY
 };
 
-class Savepoint
+class CPPCONN_PUBLIC_FUNC Savepoint
 {
   /* Prevent use of these */
   Savepoint(const Savepoint &);

test/CJUnitTestsPort/simple/BlobTest.cpp

@@ -123,8 +123,8 @@ void BlobTest::tearDown()
 
     if ( asString )
     {
-      sql::SQLString str;
-      testBlobFile->readFile( const_cast<std::string&>(str.asStdString()) );
+      std::string str;
+      testBlobFile->readFile(str);
 
       pstmt->setString( 1, str );
       pstmt->execute();