ability to attach to a process using pid

[Vipul-Cariappa]

Fixes #28

Test with

// pid_example.c

#include <unistd.h>
#include <stdio.h>


void func_to_debug(int argc, char *argv[]) {
    if (argc > 1) {
        for (int i = 1; i < argc; i++) {
            printf("%s\n", argv[i]);
        }
    } else {
        printf("No Arguments\n");
    }
}

int main(int argc, char *argv[]) {
    printf("pid: %d\n", getpid());
    getchar();
    func_to_debug(argc, argv);
    return 0;
}

Set a breakpoint at func_to_debug after launching idd. Then continue execution. getchar is used to suspend execution, to attach gdb.

---

The initial two commits in this PR are related to the old PR (parallel execution using multiprocessing).
They were small changes, so I thought of combining them.

[vgvassilev]

Lgtm!