asan: readelf: memory leaks

asan: readelf: memory leaks

This tidies some code used by readelf, hopefully fixing some
intermittent oss-fuzz bug reports that likely could only be reproduced
by feeding readelf two or more object files on the command line.  The
second and subsequent file may see non-zero state in .bss variables,
and non-initial values in .data variables.  This patch fixes some of
those, and moves some .data variables to .rodata.

	* dwarf.c (frame_display_row): Do without static variable "sloc".
	(cu_tu_indexes_read): Move to file scope.
	(free_debug_memory): Reset it here, along with level_type_signed.
	Free and clear a number of other static variables.
	* readelf.c (arm_attr_public_tag <table>): Constify, updating..
	(arm_attr_tag_*): ..all these uses.
	(process_mips_specific): Free "rels" on error path.