Adapted a number of proposed patches:
   - Badari Pulavarty of IBM's implentation of support for 2.6.14
     ppc64 kernel's use of 4-level page tables.
   - Added a new "extensions" sub-directory for collecting crash
     command extension libaries; initially populated with the sample
     "echo.c" from the extend help page, along with a device-mapper
     related "dminfo.c" module from NEC.
   - Castor Fu of 3PAR's implementation of support for LKCD version 10,
     as well the handling of single-bit errors in LKCD compressed
     pages by trying out all possible single-bit errors.  Also his
     fixes for better recognizing -fomit-frame-pointer kernel builds,
     a stronger defense against potential bogus processor numbers
     associated with tasks in dumpfiles, and a fix to re-allow crash
     builds for gcc 2.x compilers.
   Fix for potential "vmcore: initialization failed" fatal error during
   initializaton when using more than just a vmlinux and vmcore command
   line arguments.
   Fix for diskdump.c compile failures using gcc 2.96.
   Update to the x86_64 pseudo-backtrace code to show as a frame the
   RSP, RIP and name of the function causing a kernel-mode exception
   frame.
   Fix for the x86_64 pseudo-backtrace code to not neglect to show the
   user-mode exception frame when that task subsequently took a
   kernel-mode exception.
   Exported the load_extension() and unload_extension() functions so
   that they can be called from an extension library.