Allow fio headers to be included by a C++ build

Allow fio headers to be included by a C++ build

The attached patch allows fio 1.17.2 header files to be included by a
C++ build without generating compile errors due to C-ism.
Specifically, due to:
- use of the keyword "new" as a parameter name
- a cast of a return value to void *, when the function signature
returns a different type

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>