Adds /utf-8 to compile options

Signed-off-by: Nathan Hjelm <hjelmn@me.com>
diff --git a/msvc/libusb_static_2015.vcxproj b/msvc/libusb_static_2015.vcxproj
index d39d5df..7910967 100644
--- a/msvc/libusb_static_2015.vcxproj
+++ b/msvc/libusb_static_2015.vcxproj
@@ -45,6 +45,7 @@
   </PropertyGroup>
   <ItemDefinitionGroup>
     <ClCompile>
+      <AdditionalOptions>/utf-8 %(AdditionalOptions)</AdditionalOptions>
       <AdditionalIncludeDirectories>.;..\libusb;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <PreprocessorDefinitions>WINVER=0x0501;_WIN32_WINNT=0x0501;_LIB;_CRT_SECURE_NO_WARNINGS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ProgramDataBaseFileName>$(IntDir)$(TargetName).pdb</ProgramDataBaseFileName>