variable hz is defined as a macro in AIX system header
    /usr/include/sys/m_param.h (as "ticks per second of the clock").
    The pre-processor replaces hz with the numeric value defined in
    system header file and therefore emits an error.
    Re-naming variable name to "iz".

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2104483002
Cr-Commit-Position: refs/heads/master@{#37308}