add flag to detect if using the modified API

Expose dlpi_name and dlpi_addr in syminfo callback

libbacktrace: check for sys/link.h

QNX uses sys/link.h rather than link.h for dl_iterate_phdr

Fixes #86

	* configure.ac: Check for sys/link.h.  Use either link.h or
	sys/link.h when checking for dl_iterate_phdr.
	* elf.c: Include sys/link.h if available.
	* configure, config.h.in: Regenerate.

libbacktrace: don't exit Mach-O dyld library loop on one failure

	* macho.c (backtrace_initialize) [HAVE_MACH_O_DYLD_H]: Don't exit
	loop if we can't find debug info for one shared library.

For #85

libbacktrace: don't let "make clean" remove allocfail.sh

	* Makefile.am (MAKETESTS): New variable split out of TESTS.
	(CLEANFILES): Replace TESTS with BUILDTESTS and MAKETESTS.
	* Makefile.in: Regenerate.

Fixes #81

libbacktrace: replace fgrep with grep in configure script

Patch by Xi Ruoyao.

	* configure.ac: Use grep instead of fgrep.
	* configure: Regenerate.

libbacktrace: don't skip initial aligned byte in uncompressed block

Patch from Rui Ueyama, who says:

libbacktrace occasionally fails to decompress compressed debug info
even though the sections contain valid zlib streams. The cause of the
issue is an off-by-one error.

If a zlib data block is a plain data (uncompressed data), the next two
bytes contain the size of the block. These two bytes value is byte-
aligned, so if we read-ahead more than 8 bits, we need to unread it.

So, the correct condition to determine whether or not we need to
unread a byte is bits >= 8 and not bits > 8. Due to this error,
if the last read bits happened to end at a byte boundary, the next
byte would be skipped. That caused the decompression failure.

This bug was originally reported against the mold linker.
rui314/mold#402

	* elf.c (elf_zlib_inflate): Don't skip initial aligned byte in
	uncompressed block.

libbacktrace: gather address ranges from skeleton units

	* dwarf.c (find_address_ranges): Handle skeleton units.
	(read_function_entry): Likewise.

libbacktrace: initialize DWARF 5 fields of unit

When I added the fields in 2019-12-13 I forgot to initialize them.

	* dwarf.c (build_address_map): Initialize DWARF 5 fields of unit.

configury: support --disable-werror

configury: update to recent versions

Copied from GCC tip.

Fixes #84

config/override.m4: don't require exactly autoconf 2.69

Fixes #71
Fixes #74

libbacktrace: don't special case file 0

It's no longer necessary as file 0 is now set up in all cases.

	* dwarf.c (read_line_program): Don't special case file 0.
	(read_function_entry): Likewise.

Fixes #69

libbacktrace: pass -1 to error callback for unrecognized DWARF

	PR libbacktrace/98818
	* dwarf.c (dwarf_buf_error): Add errnum parameter.  Change all
	callers.
	* backtrace.h: Update backtrace_error_callback comment.

libbacktrace: check for objcopy --add-gnu-debuglink using --help

	* configure.ac: Check for objcopy --add-gnu-debuglink by using
	objcopy --help.
	* configure: Regenerate

libbacktrace: don't fail tests if dwz fails

	* Makefile.am (%_dwz): If dwz fails, use uncompressed debug info.
	* Makefile.in: Regenerate.

libbacktrace: use correct directory/filename for DWARF 5

	PR debug/98716
	* dwarf.c (read_v2_paths): Allocate zero entry for dirs and
	filenames.
	(read_line_program): Remove parameter u, change caller.  Don't
	subtract one from dirs and filenames index.
	(read_function_entry): Don't subtract one from filenames index.

Update copyright years.

libbacktrace: correct buffer overflow tests

	* dwarf.c (resolve_string): Use > rather than >= to check whether
	string index extends past buffer.
	(resolve_addr_index): Similarly for address index.

libbacktrace: update README