[MERGE #401] Page allocator used by CustomHeap's metadata don't need standing free page
[MERGE #401] Page allocator used by CustomHeap's metadata don't need standing free page

Merge pull request #401 from curtisman:freepage
The CustomHeap metadata isn't very big and we don't allocate them too often.
So we don't need standing free page for it (i.e. only commit if a page is in use)

mrkmarron/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore