Rework the routines that convert AP[S]Int into a string.  Now, instead of
returning an std::string by value, it fills in a SmallString/SmallVector
passed in.  This significantly reduces string thrashing in some cases.

More specifically, this:
 - Adds an operator<< and a print method for APInt that allows you to 
   directly send them to an ostream.
 - Reimplements APInt::toString to be much simpler and more efficient
   algorithmically in addition to not thrashing strings quite as much.

This speeds up llvm-dis on kc++ by 7%, and may also slightly speed up the
asmprinter.  This also fixes a bug I introduced into the asmwriter in a
previous patch w.r.t. alias printing.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54873 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AsmParser/ParserInternals.h b/lib/AsmParser/ParserInternals.h
index aae1d53..cc35038 100644
--- a/lib/AsmParser/ParserInternals.h
+++ b/lib/AsmParser/ParserInternals.h
@@ -170,7 +170,7 @@
     case GlobalID      : return '@' + utostr(Num);
     case LocalName     : return *Name;
     case GlobalName    : return *Name;
-    case ConstAPInt    : return ConstPoolInt->toString();
+    case ConstAPInt    : return ConstPoolInt->toString(10);
     case ConstFPVal    : return ftostr(*ConstPoolFP);
     case ConstNullVal  : return "null";
     case ConstUndefVal : return "undef";