Add a catch for std::length_error for the case where the string can't handle 2GB. (like say 32-bit big-endian)

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@325147 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/input.output/stream.buffers/streambuf/streambuf.protected/streambuf.put.area/pbump2gig.pass.cpp

@@ -38,6 +38,7 @@ int main()
         assert(sb.pubpbase() <= sb.pubpptr());
 #ifndef TEST_HAS_NO_EXCEPTIONS
     }
-	catch (const std::bad_alloc &) {}
+    catch (const std::length_error &) {} // maybe the string can't take 2GB
+    catch (const std::bad_alloc    &) {} // maybe we don't have enough RAM
 #endif
 }