BitVector tweaks.

- Double the vector's capacity when growing to avoid unneeccesary reallocation.
- Do the reallocation with realloc(3) which can expand the memory in place.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120183 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed