Cache and retrieve syscall arguments when needed.
* runtime/task_finder.c (__stp_utrace_task_finder_target_syscall_entry):
New function that caches syscall arguments for mmap(), munmap(), and
mprotect() for use in __stp_utrace_task_finder_target_syscall_exit().
(__stp_utrace_task_finder_target_syscall_exit): Uses cached syscall
argument info when making callbacks.
(stap_start_task_finder): Initializes map subsytem for storing syscall
argument data.
* runtime/task_finder_map.c: New file containing functions to save and
retrieve syscall arguments.