[PATCH] Initial DWARF64 support for .debug_line

[Ed Maste]

  This patch addresses the output of GCC and gas on FreeBSD mips64
  ```
  # gcc --version
  gcc (GCC) 4.2.1 20070831 patched [FreeBSD]
  # as --version
  GNU assembler 2.17.50 [FreeBSD] 2007-07-03
  ```

  This toolchain generally outputs dwarf2 but uses the 64-bit format from dwarf3.  This is the format that uses 0xffffffff in the initial length field, followed by a 64-bit length, and 64-bit offsets throughout.  Equivalent support already exists in DWARFDebugFrame.cpp.

  My testcase binary is tiny; 64-bit is not necessary.  The (older) version of GCC and gas in FreeBSD output this format for some reason; I do not know if more recent versions still do.



  for whatever reason the toolchain insists on

http://llvm-reviews.chandlerc.com/D1988