[WinEH] Emit EH tables for __CxxFrameHandler3 on 32-bit x86

Small (really small!) C++ exception handling examples work on 32-bit x86
now.

This change disables the use of .seh_* directives in WinException when
CFI is not in use. It also uses absolute symbol references in the tables
instead of imagerel32 relocations.

Also fixes a cache invalidation bug in MMI personality classification.

llvm-svn: 238575

llvm/lib/CodeGen/MachineModuleInfo.cpp

@@ -308,6 +308,7 @@ void MachineModuleInfo::EndFunction() {
 
   // Clean up exception info.
   LandingPads.clear();
+  PersonalityTypeCache = EHPersonality::Unknown;
   CallSiteMap.clear();
   TypeInfos.clear();
   FilterIds.clear();