Revert "Revert "Modify FPFeatures to use delta not absolute settings""

This reverts commit b55d723ed61052b77e720dcffecac43abe873186.
Reapply Modify FPFeatures to use delta not absolute settings

To solve https://bugs.llvm.org/show_bug.cgi?id=46166 where the
floating point settings in PCH files aren't compatible, rewrite
FPFeatures to use a delta in the settings rather than absolute settings.
With this patch, these floating point options can be benign.

Reviewers: rjmccall

Differential Revision: https://reviews.llvm.org/D81869
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 2a17360..6f364df 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -3960,7 +3960,7 @@
 }
 
 /// Write an FP_PRAGMA_OPTIONS block for the given FPOptions.
-void ASTWriter::WriteFPPragmaOptions(const FPOptions &Opts) {
+void ASTWriter::WriteFPPragmaOptions(const FPOptionsOverride &Opts) {
   RecordData::value_type Record[] = {Opts.getAsOpaqueInt()};
   Stream.EmitRecord(FP_PRAGMA_OPTIONS, Record);
 }
@@ -4790,7 +4790,7 @@
   WriteReferencedSelectorsPool(SemaRef);
   WriteLateParsedTemplates(SemaRef);
   WriteIdentifierTable(PP, SemaRef.IdResolver, isModule);
-  WriteFPPragmaOptions(SemaRef.getCurFPFeatures());
+  WriteFPPragmaOptions(SemaRef.CurFPFeatureOverrides());
   WriteOpenCLExtensions(SemaRef);
   WriteOpenCLExtensionTypes(SemaRef);
   WriteCUDAPragmas(SemaRef);