PR other/67457
* backtrace.c: #include "internal.h".
(struct backtrace_data): Add can_alloc field.
(unwind): If can_alloc is false, don't try to get file/line
information.
(backtrace_full): Set can_alloc field in bdata.
* alloc.c (backtrace_alloc): Don't call error_callback if it is
NULL.
* mmap.c (backtrace_alloc): Likewise.
* internal.h: Update comments for backtrace_alloc and
backtrace_free.
From-SVN: r227533
