As in r11-5449, this adds a muliplier to the timeout for slow tests.
This covers the majority of the <regex> and PSTL tests.
libstdc++-v3/ChangeLog:
* testsuite/20_util/specialized_algorithms/pstl/*: Add
dg-timeout-factor.
* testsuite/25_algorithms/pstl/*: Likewise.
* testsuite/26_numerics/pstl/*: Likewise.
* testsuite/28_regex/*: Likewise.