Fix uninitialized variables and bad function calls

[CJxD]

usecs_to_cputime64 doesn't seem to exist anymore, so I replaced it with a macro I found while browsing the linux source code suggesting that there is 4096 cputime per microsecond. May not apply to all platforms though perhaps?

Also, I'm getting a segfault when I actually try this code out. I don't think these changes would cause that though. I'm running 4.15.0-36.