Workaround 'local variable end shadows outer symbol' cppcheck warnings

Workaround 'local variable end shadows outer symbol' cppcheck warnings

* include/private/gcconfig.h [SPARC && FREEBSD] (end): Do not declare
external variable if CPPCHECK.
* include/private/gcconfig.h [MIPS && EWS4800 && (!_MIPS_SZPTR
|| _MIPS_SZPTR!=64)] (end): Likewise.
* include/private/gcconfig.h [ALPHA && FREEBSD] (end): Likewise.
* include/private/gcconfig.h [!DATAEND] (end): Likewise.
* include/private/gcconfig.h [I386 && RTEMS] (end): Do not declare
(because it automatically declared in DATAEND is undefined).
* include/private/gcconfig.h [I386 && RTEMS] (DATAEND): Do not define.
* include/private/gcconfig.h [MIPS && EWS4800]: Adjust indentation.