+ Fixed merge of cells to retain value in upper left cell+ Replaced std::map::at() with iterators and find. Removed some superfluous calls to std::map::find()

+ Visual Studio fixes
+ Fixed return values
+ Removed unused variables

src/Mod/Spreadsheet/App/PreCompiled.h

@@ -33,14 +33,16 @@
 # define SpreadsheetExport
 #endif
 
-#ifdef _PreComp_
 /// here get the warnings of to long specifieres disabled (needed for VC6)
 #ifdef _MSC_VER
-#	pragma warning( disable : 4251 )
-#	pragma warning( disable : 4503 )
-#	pragma warning( disable : 4786 )  // specifier longer then 255 chars
+#   pragma warning( disable : 4251 )
+#   pragma warning( disable : 4275 )
+#   pragma warning( disable : 4503 )
+#   pragma warning( disable : 4786 )  // specifier longer then 255 chars
 #endif
 
+#ifdef _PreComp_
+
 // standard
 #include <iostream>
 #include <sstream>