Use proper types from <sys/types.h> in struct definition

[pythonhacker]

I noticed a few places where int types are used when standard system typedefs are available which would be more appropriate.

Examples.

1. fields pid, ppid in struct Process. Should be pid_t instead of "unsigned int".
2. field uid etc - Should be uid_t.
3. field create_time - Should be time_t (I think).

Most of these are available in <sys/types.h> and we should use them wherever possible.

[nibrahim]

I'm not completely sure about this. We'd have different types for different platforms. The types like pid_t are Linux specific. Are they not?

[pythonhacker]

It is part of C POSIX library. Not specific to Linux. If you have a proper autoconfigure system it can decide to add or not add it for you depending on the target platform.

https://en.wikipedia.org/wiki/C_POSIX_library

[k4rtik]

I took care of pid_t type fields in the last refactor (nibrahim@ad7964a).