Use std::vector in syscall_catchpoint

Use std::vector in syscall_catchpoint

This changes syscall_catchpoint to use a std::vector rather than a VEC
for "syscalls_to_be_caught".  This simplifies the code a bit.

ChangeLog
2017-07-22  Tom Tromey  <tom@tromey.com>

	* break-catch-syscall.c (syscall_catchpoint)
	<syscalls_to_be_caught>: Now a std::vector<int>
	(~syscall_catchpoint): Remove.
	(insert_catch_syscall, remove_catch_syscall)
	(breakpoint_hit_catch_syscall, print_one_catch_syscall)
	(print_mention_catch_syscall, print_recreate_catch_syscall):
	Update.
	(create_syscall_event_catchpoint): Change type of "filter"
	parameter.
	(catch_syscall_split_args): Return a std::vector.
	(catch_syscall_command_1, catching_syscall_number_1): Update.