According to MSVC manual (*1), cl.exe can skip including a header file
when that:

- contains #pragma once, or
- starts with #ifndef, or
- starts with #if ! defined.

GCC has a similar trick (*2), but it acts more stricter (e. g. there
must be _no tokens_ outside of #ifndef...#endif).

Sun C lacked #pragma once for a looong time.  Oracle Developer Studio
12.5 finally implemented it, but we cannot assume such recent version.

This changeset modifies header files so that each of them include
strictly one #ifndef...#endif.  I believe this is the most portable way
to trigger compiler optimizations. [Bug #16770]

*1: https://docs.microsoft.com/en-us/cpp/preprocessor/once
*2: https://gcc.gnu.org/onlinedocs/cppinternals/Guard-Macros.html

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  the basis of base addresses comparison.

* addr2line.c: use uintptr_t instead of intptr_t for poinrters.

* addr2line.c (rb_dump_backtrace_with_lines): don't use syms.

* vm_dump.c (rb_print_backtrace): ditto.

* addr2line.h: ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45425 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

  doesn't define it. USE_ELF is already provided by configure.
  patched by Naohisa Goto. [ruby-dev:44066] [Bug #4998]

* addr2line.h: ditto.

* vm_dump.c: ditto.

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  functions in backtrace. [ruby-dev:42625]
  a patch from shinichiro.h <shinichiro.hamaji AT gmail.com>

* addr2line.h: ditto.

* common.mk: add addr2line.$(OBJEXT).

* configure.in: check dl_iterate_phdr.

* vm_dump.c (rb_vm_bugreport): use rb_dump_backtrace_with_lines in
  addr2line.c when the binary is ELF.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@29940 b2dd03c8-39d4-4d8f-98ff-823fe69b080e