Add -cc1 option -fno-diagnostics-use-presumed-location, a handy mode for
working with preprocessed testcases. This causes source locations in
diagnostics to point at the spelling location instead of the presumed location,
while still keeping the semantic effects of the line directives (entering and
leaving system-header mode, primarily).

llvm-svn: 168004
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 31dcb23..1da462a 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -538,6 +538,7 @@
   
   Opts.ShowSourceRanges = Args.hasArg(OPT_fdiagnostics_print_source_range_info);
   Opts.ShowParseableFixits = Args.hasArg(OPT_fdiagnostics_parseable_fixits);
+  Opts.ShowPresumedLoc = !Args.hasArg(OPT_fno_diagnostics_use_presumed_location);
   Opts.VerifyDiagnostics = Args.hasArg(OPT_verify);
   Opts.ElideType = !Args.hasArg(OPT_fno_elide_type);
   Opts.ShowTemplateTree = Args.hasArg(OPT_fdiagnostics_show_template_tree);