Update from gcc trunk version of libbacktrace at svn rev 256427. (#8)

Includes (among other things) support for compressed debug sections,
a variety of bugfixes, and expanded test coverage.

Makefile.am

@@ -1,5 +1,5 @@
 # Makefile.am -- Backtrace Makefile.
-# Copyright (C) 2012-2016 Free Software Foundation, Inc.
+# Copyright (C) 2012-2018 Free Software Foundation, Inc.
 
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
@@ -29,11 +29,14 @@
 # IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 # POSSIBILITY OF SUCH DAMAGE.
 
+ACLOCAL_AMFLAGS = -I .. -I ../config
+
 AM_CFLAGS = $(EXTRA_FLAGS) $(WARN_FLAGS) $(PIC_FLAG)
 
-lib_LTLIBRARIES = libbacktrace.la
 include_HEADERS = backtrace.h backtrace-supported.h
 
+noinst_LTLIBRARIES = libbacktrace.la
+
 libbacktrace_la_SOURCES = \
 	backtrace.h \
 	atomic.c \
@@ -53,7 +56,8 @@ BACKTRACE_FILES = \
 FORMAT_FILES = \
 	elf.c \
 	pecoff.c \
-	unknown.c
+	unknown.c \
+	xcoff.c
 
 VIEW_FILES = \
 	read.c \
@@ -85,7 +89,7 @@ TESTS = $(check_PROGRAMS)
 
 if NATIVE
 
-btest_SOURCES = btest.c
+btest_SOURCES = btest.c testlib.c
 btest_CFLAGS = $(AM_CFLAGS) -g -O
 btest_LDADD = libbacktrace.la
 
@@ -96,6 +100,64 @@ stest_LDADD = libbacktrace.la
 
 check_PROGRAMS += stest
 
+ztest_SOURCES = ztest.c testlib.c
+ztest_CFLAGS = -DSRCDIR=\"$(srcdir)\"
+ztest_LDADD = libbacktrace.la
+
+if HAVE_ZLIB
+ztest_LDADD += -lz
+endif
+ztest_LDADD += $(CLOCK_GETTIME_LINK)
+
+check_PROGRAMS += ztest
+
+edtest_SOURCES = edtest.c edtest2_build.c testlib.c
+edtest_LDADD = libbacktrace.la
+
+check_PROGRAMS += edtest
+
+edtest2_build.c: gen_edtest2_build; @true
+gen_edtest2_build: $(srcdir)/edtest2.c
+	cat $(srcdir)/edtest2.c > tmp-edtest2_build.c
+	$(SHELL) $(srcdir)/move-if-change tmp-edtest2_build.c edtest2_build.c
+	echo timestamp > $@
+
+if HAVE_PTHREAD
+
+check_PROGRAMS += ttest
+
+ttest_SOURCES = ttest.c testlib.c
+ttest_CFLAGS = $(AM_CFLAGS) -pthread
+ttest_LDADD = libbacktrace.la
+
+endif HAVE_PTHREAD
+
+if HAVE_OBJCOPY_DEBUGLINK
+
+TESTS += dtest
+
+dtest: btest
+	$(OBJCOPY) --only-keep-debug btest btest.debug
+	$(OBJCOPY) --strip-debug --add-gnu-debuglink=btest.debug btest dtest
+
+endif HAVE_OBJCOPY_DEBUGLINK
+
+if HAVE_COMPRESSED_DEBUG
+
+ctestg_SOURCES = btest.c testlib.c
+ctestg_CFLAGS = $(AM_CFLAGS) -g
+ctestg_LDFLAGS = -Wl,--compress-debug-sections=zlib-gnu
+ctestg_LDADD = libbacktrace.la
+
+ctesta_SOURCES = btest.c testlib.c
+ctesta_CFLAGS = $(AM_CFLAGS) -g
+ctesta_LDFLAGS = -Wl,--compress-debug-sections=zlib-gabi
+ctesta_LDADD = libbacktrace.la
+
+check_PROGRAMS += ctestg ctesta
+
+endif
+
 endif NATIVE
 
 # We can't use automake's automatic dependency tracking, because it
@@ -112,8 +174,8 @@ endif NATIVE
 
 alloc.lo: config.h backtrace.h internal.h
 backtrace.lo: config.h backtrace.h internal.h
-btest.lo: backtrace.h backtrace-supported.h
-dwarf.lo: config.h backtrace.h internal.h
+btest.lo:  backtrace.h backtrace-supported.h filenames.h
+dwarf.lo: config.h filenames.h backtrace.h internal.h
 elf.lo: config.h backtrace.h internal.h
 fileline.lo: config.h backtrace.h internal.h
 mmap.lo: config.h backtrace.h internal.h
@@ -128,3 +190,5 @@ sort.lo: config.h backtrace.h internal.h
 stest.lo: config.h backtrace.h internal.h
 state.lo: config.h backtrace.h backtrace-supported.h internal.h
 unknown.lo: config.h backtrace.h internal.h
+xcoff.lo: config.h backtrace.h internal.h
+