StlAllocator.h + MakeUnique.h -> Memory.h
Summary:
Go with the fat header approach. Merge these two into Memory.h. We could, potentially, include Malloc.h as well, but it fbstring header uses the once define for some special magic. Leave it alone for now.
An alternate approach might be moving all three leaner headers into a `memory/` subdir with `folly/Memory.h` just #including the three.
Test Plan:
fbconfig folly/tests && fbmake runtests_opt
Reviewed By: delong.j@fb.com
FB internal diff:
D745873