file origins
------------

- bits/gstdint.h:   manually created
- bits/gthr.h:      renamed copy of 'libgcc/gthr-single.h' from GCC source
- bits/c++config.h:
  - run 'make noux-pkg/gcc_x86' for a 32-bit x86 platform
  - run 'make noux-pkg/gcc_x86' for a 64-bit x86 platform
  - run 'make noux-pkg/gcc_arm' for a 32-bit ARM platform
  - compare the generated 'c++config.h' files
  - create a combined 'c++config.h' file by making the differing macros
    depend on the '__x86_64__' and '__ARM_EABI__' macros
