Fix PE/COFF resource merging problems. There were two issues:
1. Strings (and then resource data) must follow immediately after
the end of the tables.
2. Units of resource data must be 8-byte aligned.
PR ld/16807
* peXXigen.c (struct rsrc_regions): New structure.
(rsrc_print_resource_directory): Use new structure. Include
offset of directory in listing.
(rsrc_print_resource_entry): Likewise.
(rsrc_print_section): Likewise.
(rsrc_count_entries): Do not increment sizeof_strings or
sizeof_leaves.
(rsrc_count_directory): Do not increment sizeof_tables.
(rsrc_compute_region_sizes): New function.
(rsrc_write_leaf): Maintain 8-byte alignment for resource data.
(rsrc_process_section): Compute size of regions after merging
entries.