more c++20 changes

[anonrig]

Before landing, let's benchmark these changes first.

Before

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Benchmark                                  Time             CPU   Iterations        GHz cycle/byte cycles/url instructions/byte instructions/cycle instructions/ns instructions/url     ns/url      speed  time/byte   time/url      url/s
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
BasicBench_AdaURL_href                  2153 ns         2153 ns       320225    4.96471    12.2248   1.17222k           54.5643            4.46341         22.1595         5.23211k    236.111 400.773M/s  2.49518ns   239.26ns 4.17956M/s
BasicBench_AdaURL_aggregator_href       1325 ns         1325 ns       528206     6.2136          9        863           40.2665            4.47406            27.8         3.86111k    138.889 651.459M/s  1.53502ns  147.191ns  6.7939M/s
BasicBench_AdaURL_CanParse               941 ns          941 ns       746802    7.36229    7.46466    715.778           32.5736            4.36371         32.1269         3.12344k    97.2222 916.842M/s   1.0907ns  104.586ns  9.5615M/s
BasicBench_whatwg                       4290 ns         4290 ns       163228    4.04824    19.9363   1.91167k           97.5458            4.89288         19.8075         9.35356k    472.222 201.168M/s  4.97097ns  476.661ns 2.09793M/s
BasicBench_CURL                        10923 ns        10923 ns        64140    3.55464    44.6246     4.279k           218.458            4.89546         17.4016         20.9477k   1.20378k 79.0072M/s  12.6571ns  1.21367us 823.945k/s

After

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Benchmark                                  Time             CPU   Iterations        GHz cycle/byte cycles/url instructions/byte instructions/cycle instructions/ns instructions/url     ns/url      speed  time/byte   time/url      url/s
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
BasicBench_AdaURL_href                  2114 ns         2114 ns       329982    4.74682    11.6883   1.12078k           54.4114             4.6552         22.0974         5.21744k    236.111 408.175M/s  2.44993ns  234.921ns 4.25675M/s
BasicBench_AdaURL_aggregator_href       1316 ns         1316 ns       532931    5.98296    8.95017    858.222           40.2317            4.49508         26.8939         3.85778k    143.444 655.743M/s  1.52499ns  146.229ns 6.83857M/s
BasicBench_AdaURL_CanParse               927 ns          927 ns       756086    7.08914    7.18772    689.222           32.5075            4.52265         32.0617         3.11711k    97.2222 931.106M/s  1.07399ns  102.984ns 9.71026M/s
BasicBench_whatwg                       4222 ns         4222 ns       165047    4.06739    19.4415   1.86422k           97.5666            5.01848         20.4121         9.35556k    458.333  204.41M/s  4.89212ns    469.1ns 2.13174M/s
BasicBench_CURL                        10893 ns        10893 ns        64409    3.53916    44.0857   4.22733k           218.525            4.95682          17.543         20.9541k   1.19444k 79.2276M/s  12.6219ns   1.2103us 826.244k/s

[lemire]

@anonrig My comments were confused above. I still recommend you change the update_base_search function signature if you are expecting an r-value.