CLD should check result of "new" in all use cases

[GoogleCodeExporter]

There are many uses of the "new" operator in the CLD source code, such as in 
scoreonescriptspan.cc's "new ScoringHitBuffer":

https://code.google.com/p/cld2/source/browse/trunk/internal/scoreonescriptspan.c
c#1168

There's no check that the "new" operator successfully allocated memory. In 
low-memory conditions this can lead to an access violation and subsequent crash.

The code should fail gracefully under low-memory conditions, though it isn't 
immediately obvious how to "gracefully" fail or how helpful it would be to the 
caller to have such behavior if they are truly out of memory.

Original issue reported on code.google.com by andrewha...@google.com on 7 Jan 2015 at 12:19