Class-ify lm_info_svr4

This patch makes lm_info_svr4 a "real" class.  It initializes fields,
uses bool and replaces XCNEW/xfree with new/delete.

The memcpy in svr4_copy_library_list is replaced by a usage of the
default copy constructor.

gdb/ChangeLog:

	* solib-svr4.h (struct lm_info_svr4): Initialize fields.
	<l_addr_p>: Change type to bool.
	* solib-svr4.c (lm_info_read): Allocate lm_info_svr4 with new.
	(svr4_free_so): Free lm_info_svr4 with delete.
	(svr4_copy_library_list): Replace memcpy with call to copy
	constructor.
	(library_list_start_library, svr4_default_sos): Allocate
	lm_info_svr4 with new.