Re: pgbench's expression parsing & negative numbers

The following review has been posted through the commitfest application:
make installcheck-world:  not tested
Implements feature:       tested, passed
Spec compliant:           tested, passed
Documentation:            not tested

Patch does not apply cleanly on the master branch, anyways I managed that.  Patch work according to specs, and no issue found. 
The only minor nit is that you can keep the full comments of function strtoint64

/*
 * If not errorOK, an error message is printed out.
 * If errorOK is true, just return "false" for bad input.
 */