[llvm-readobj] Make some commonly used short options visibile in -help

[MaskRay]

For people who think llvm-readelf is a replacement of readelf, they would like to see -d -r ... listed in llvm-readelf -help. It also helps understanding the confusing -s (which is unfortunately different in semantics but I haven't dug up the original intention). They at least have some way to know they are different...

[ruiu]

LGTM

tools/llvm-readobj/llvm-readobj.cpp

 }
 
 int main(int argc, const char *argv[]) {
   InitLLVM X(argc, argv);
 
   // Register the target printer for --version.
   cl::AddExtraVersionPrinter(TargetRegistry::printRegisteredTargetsForVersion);
 
+  // Make some commonly used short options visibile in -help.
+  opts::DynamicTableShort.setHiddenFlag(cl::NotHidden);
+  opts::FileHeadersShort.setHiddenFlag(cl::NotHidden);
+  opts::RelocationsShort.setHiddenFlag(cl::NotHidden);
+  opts::SectionsShort.setHiddenFlag(cl::NotHidden);
+  opts::SectionsShortUpper.setHiddenFlag(cl::NotHidden);
+  opts::SymbolsShort.setHiddenFlag(cl::NotHidden);
+
   opts::WideOutput.setHiddenFlag(cl::Hidden);
 
   if (sys::path::stem(argv[0]).find("readelf") != StringRef::npos)
     opts::Output = opts::GNU;
 
   cl::ParseCommandLineOptions(argc, argv, "LLVM Object Reader\n");
 
   // Default to stdin if no filename is specified.