Different Tcl error result generation in OnScriptError() implementation.

* line number starts at 1
* consider BSTR length when appending to Tcl error result
Decreased version number to 0.15
Added the 2 .tcl files to the Visual Studio project.
Rename axsh-string-guid-util.c/.h to axsh-util.c/.h as it gets more general.
Moved AXSH_SetTclResultToVARIANT() code to new function AXSH_VariantToTclObj().