stack-trace: New module. * lib/stdlib.in.h (print_stack_trace): Make part of the stack-trace module. * lib/stack-trace-impl.h: New file, based on lib/abort-debug.c. * lib/stack-trace.c: New file, based on lib/abort-debug.c. * lib/abort-debug.c: Include stack-trace-impl.h. Remove definitions moved to stack-trace-impl.h. (print_stack_trace): Remove function. * m4/stdlib_h.m4 (gl_STDLIB_H_REQUIRE_DEFAULTS): Initialize GNULIB_STACK_TRACE. (gl_STDLIB_H_DEFAULTS): Initialize CAN_PRINT_STACK_TRACE. * m4/stack-trace.m4: New file, based on m4/abort-debug.m4. * m4/abort-debug.m4 (gl_ABORT_DEBUG_EARLY): Remove macro. (gl_ABORT_DEBUG): Require gl_STDLIB_H_DEFAULTS, gl_STACK_TRACE_EARLY. Set REPLACE_ABORT here. * modules/stdlib (Makefile.am): Substitute GNULIB_STACK_TRACE, CAN_PRINT_STACK_TRACE. * modules/stack-trace: New file. * modules/abort-debug (Depends-on): Add stack-trace. Remove execinfo. (configure.ac-early): Remove section. * DEPENDENCIES: Update.