Log Message:
Changes 1.7.69:
* Check for NULL return from malloc().
* Undefine CLOCKS_PER_SECOND "1000" found in some version of MinGW.
* Replaced most "atoi(argv[++i])" with "pngcrush_get_long" \ 
which does
    "BUMP_I; strtol(argv[i],ptr,10)" and added pngcrush_check_long macro
    to detect malformed or missing parameters (debian bug 716149).
* Added global_things_have_changed=1 when reading -bkgd.
* The "-bit_depth N" option did not work reliably and has been removed.