When not using Makefile, e.g. with MSVC, if hardware
supports BMI2 instructions, then USE_PEXT should be
added in project configuration to enable pext support.
No functional change.
///
/// -DUSE_POPCNT | Add runtime support for use of popcnt asm-instruction. Works
/// | only in 64-bit mode and requires hardware with popcnt support.
+///
+/// -DUSE_PEXT | Add runtime support for use of pext asm-instruction. Works
+/// | only in 64-bit mode and requires hardware with pext support.
#include <cassert>
#include <cctype>