[tnozaki-elftoolchain] replace FreeBSD's libelf/libdwarf to elftoolchain's one

[Takehiko NOZAKI]

T/O

[Takehiko NOZAKI]

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• Issue #273 - TNF local patch for libelf _libelf_host_byteorder() to determin host endian on the fly in a portable way
• Issue #274 - TNF local patch for libelf - elf_hash() prototype const char * -> const void *
• Issue #275: TNF local patch for libelf - LIBELF_COPY_U32/LIBELF_COPY_S32 range check
• Issue #276: TNF local patch for libelf - add miscellaneous integer overflow check
• Issue #277: TNF local patch for libelf - suppress warning unused function argument
• Issue #278: TNF local patch for libelf - suppress -Wpointer-sign, signedness mismatch _libelf_translator_function's 1st argument
• Issue #279: TNF local patch for libelf - miscellaneous lint(1) warning fix for libelf_convert.m4
• Issue #280: TNF local patch for libelf - tools build failure on Mac OS X due to missing roundup2()
• Issue #281: refactoring _libelf.h and libelf.h header file dependency
• Issue #282: TNF local patch for libelf/libdwarf - include nbtool_config.h
• Issue #283: MKDTRACE=yes build failure caused by conflict definition between sys/elfdefinitions.h and sys/exec_elf.h

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