minimize use of new and delete in engine

In the file e/newdelete.cpp, we redefine global new, delete, to call GC_MALLOC_UNCOLLECTABLE. Removing these definitions causes M2 to crash during startup (reading the m2 files). Changing these calls to GC_MALLOC_ATOMIC also causes M2 to crash.

The main problem is that one cannot have containers containing pointers to GC allocated memory, in a memory block not allocated by GC. (GC == libgc, the Boehm-Demers garbage collector that we use).

But allocating with either the built in new or GC_MALLOC_ATOMIC is faster that GC_MALLOC_UNCOLLECTABLE in inner loop code.

So: change all uses of new in engine code to something like new_atomic, new_container_containing_gc_allocated_memory.