PR27202, readelf -wL doesn't work on ".loc 0"

PR27202, readelf -wL doesn't work on ".loc 0"

For DWARF revision 4 and earlier, display_debug_lines_decoded
populates the file_table array with entries read from .debug_line
after the directory table.  file_table[0] contains the first entry.
DWARF rev 4 line number programs index this entry as file number one.
DWARF revision 5 changes .debug_line format quite extensively, and in
particular gives file number zero a meaning.

	PR 27202
	* dwarf.c (display_debug_lines_decoded): Correct indexing used
	for DWARF5 files.