Rename Common::FifoQueue to Common::SPSCQueue

Since all queues are FIFO data structures, the name wasn't informative
as to why you'd use it over a normal queue. I originally thought it had
something to do with the hardware graphics FIFO.

This renames it using the common acronym SPSC, which stands for
single-producer single-consumer, and is most commonly used to talk about
lock-free data structures, both of which this is.

Source/Core/Common/Common.vcxproj

@@ -62,7 +62,6 @@
     <ClInclude Include="DebugInterface.h" />
     <ClInclude Include="ENetUtil.h" />
     <ClInclude Include="Event.h" />
-    <ClInclude Include="FifoQueue.h" />
     <ClInclude Include="File.h" />
     <ClInclude Include="FileSearch.h" />
     <ClInclude Include="FileUtil.h" />
@@ -142,6 +141,7 @@
     <ClInclude Include="SDCardUtil.h" />
     <ClInclude Include="Semaphore.h" />
     <ClInclude Include="SettingsHandler.h" />
+    <ClInclude Include="SPSCQueue.h" />
     <ClInclude Include="StringUtil.h" />
     <ClInclude Include="Swap.h" />
     <ClInclude Include="SymbolDB.h" />
@@ -237,4 +237,4 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>