Do not assert when reading an exponent out of range.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111534 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/APFloat.cpp

@@ -153,6 +153,7 @@ readExponent(StringRef::iterator begin, StringRef::iterator end)
     value += absExponent * 10;
     if (absExponent >= overlargeExponent) {
       absExponent = overlargeExponent;
+      p = end;  /* outwit assert below */
       break;
     }
     absExponent = value;