BUG: Fix cmSystemTools::ChangeRPath to not complain if there is no RPATH entry in the file but the requested new rpath is empty.

BUG: Do not try to change the RPATH when installing a target if CMAKE_SKIP_RPATH is on or the path does not need to be changed.

  - Add cmSystemTools::ChangeRPath method
  - Add undocumented file(CHRPATH) command
  - When installing use file(CHRPATH) to change the rpath
    instead of relinking
  - Remove CMAKE_CHRPATH lookup from CMakeFindBinUtils
  - Remove CMAKE_USE_CHRPATH option since this should
    always work

ENH: Update Preprocess test to distinguish between the make tool or compiler tool that is at fault for not supporting a particular character in definitions.  Make it skip the % character when the compiler is MSVC and it is a non-nmake tool.

ENH: make CMAKE_ALLOW_LOOSE_LOOP_CONSTRUCTS the default and remove the property.  If any value is specified in an endif, endforeach, endwhile, etc then make sure it matches the start string.  If no values are given then it is no longer an error.

  - Add support to get RPATH and RUNPATH entries.
  - Add support to get file offsets to strings.
  - Add more DT_* tags to byte swapping.

BUG: cmComputeLinkInformation::CheckImplicitDirItem needs to extract the filename portion of the link item to test against the library regex.

  - Use a response file when enabled by
    CMAKE_<LANG>_USE_RESPONSE_FILE_FOR_OBJECTS
  - Enable for C and CXX with cl (MSVC)
  - Enable for Fortran with ifort (Intel Fortran)

  - Enabled when system provides elf.h
  - Introduce cmELF class to parse ELF files
  - Use in cmSystemTools::GuessLibrarySOName to really get soname

BUG: Apply patch from bug#6445.  Add preprocessor definitions to assembly and preprocessing build rules.

ENH: Add support to C compiler identification for void return type from main.  Cross-compilers for embedded platforms may require it.

ENH:  Adjust when log is cleared.  Its kept doing generate,
      and cleared when changing the source directory.
      #6358.

apparently rpmbuild can't handle paths with spaces and can't handle
variables in comments...

Alex

  - Write a single source file into the compiler id directory
  - This avoid requiring the compiler to behave correctly with
    respect to include rules and the current working directory
  - Helps to identify cross-compiling toolchains with unusual
    default behavior

ENH: Simplify make build rule generation by removing use of OBJECTS_QUOTED and TARGET_QUOTED rule variables and updating the generation of OBJECTS to always use the newer cmLocalGenerator::Convert method.

  - Its <iosfwd> header includes windows.h which
    defines GetCurrentDirectory
  - It defines 'interface' so we cannot use it as
    a variable name.