libstdc++: Fix 28_regex/basic_regex/84110.cc on Solaris

libstdc++: Fix 28_regex/basic_regex/84110.cc on Solaris

28_regex/basic_regex/84110.cc currently FAILs on Solaris:

FAIL: 28_regex/basic_regex/84110.cc (test for excess errors)
UNRESOLVED: 28_regex/basic_regex/84110.cc compilation failed to produce executable

Excess errors:
/vol/gcc/src/hg/master/local/libstdc++-v3/testsuite/28_regex/basic_regex/84110.cc:14: error: reference to 'extended' is ambiguous

The issue is seen in the full output:

/vol/gcc/src/hg/master/local/libstdc++-v3/testsuite/28_regex/basic_regex/84110.cc: In function ‘void test01()’:
/vol/gcc/src/hg/master/local/libstdc++-v3/testsuite/28_regex/basic_regex/84110.cc:14: error: reference to ‘extended’ is ambiguous
In file included from /var/gcc/regression/master/11.4-gcc-gas/build/gcc/include-fixed/math.h:391,
                 from /var/gcc/regression/master/11.4-gcc-gas/build/i386-pc-solaris2.11/libstdc++-v3/include/cmath:45,
                 from /vol/gcc/src/hg/master/local/libstdc++-v3/include/precompiled/stdc++.h:41:
/usr/include/floatingpoint.h:73: note: candidates are: ‘typedef unsigned int extended [3]’

Fixed by disambiguating extended.  Tested on i386-pc-solaris2.11,
sparc-sun-solaris2.11, and x86_64-pc-linux-gnu.

2021-10-20  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	libstdc++-v3:
	* testsuite/28_regex/basic_regex/84110.cc (test01)
	[__cpp_exceptions]: Disambiguate extended.

(cherry picked from commit 931f1e377ad27af2801c1e68946010e980810539)