Remove some GDBSERVER checks from linux-ptrace

Remove some GDBSERVER checks from linux-ptrace

This patch removes some GDBSERVER checks from nat/linux-ptrace.c.
Currently the code uses a compile-time check to decide whether some
flags should be used.  This changes the code to instead let users of
the module specify an additional set of flags; and then changes gdb's
linux-nat.c to call this function.  At some later date, when the back
ends are fully merged, we will be able to remove this function again.

gdb/
2014-07-24  Tom Tromey  <tromey@redhat.com>
	    Gary Benson  <gbenson@redhat.com>

	* nat/linux-ptrace.c (additional_flags): New global.
	(linux_test_for_tracesysgood, linux_test_for_tracefork): Use
	additional_flags; don't check GDBSERVER.
	(linux_ptrace_set_additional_flags): New function.
	* nat/linux-ptrace.h (linux_ptrace_set_additional_flags):
	Declare.
	* linux-nat.c (_initialize_linux_nat): Call
	linux_ptrace_set_additional_flags.