Class-ify lm_info_frv

Class-ify lm_info_frv

This patches makes lm_info_frv a "real" class.  It adds a destructor,
initializes the fields and replaces XCNEW/xfree with new/delete.

gdb/ChangeLog:

	* solib-frv.c (struct lm_info_frv): Add destructor, initialize
	fields.
	(frv_current_sos): Allocate lm_info_frv with new.
	(frv_relocate_main_executable): Free lm_info_frv with delete,
	allocate with new.
	(frv_clear_solib, frv_free_so): Free lm_info_frv with delete.