lang/gcc10: Revert "fix build with clang 17"

This reverts commit eb5e051:

  lang/gcc10: fix build with clang 17

  When building lang/gcc10 with recent clang versions, which default to
  C++17, the following errors are produced:

    cfns.gperf:35:18: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
       35 | libc_name::hash (register const char *str, register unsigned int len)
          |                  ^~~~~~~~
    cfns.gperf:35:44: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
       35 | libc_name::hash (register const char *str, register unsigned int len)
          |                                            ^~~~~~~~
    ...many more of these...

  Upstream fixed this in
  https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=642dc602f89b2c11d5d833a52f37b04427a27cab,
  so apply it.

I accidentally included a patch for devel/electron25 in this commit.
That one will be split off and committed separately.

Reported by:    Gunther Nikl <gnikl@justmail.de>