prune: mark pseudorefs as reachable #668

Job	Run time
config	5s
win+VS build	0s
linux-musl (alpine)	7m 20s
linux32 (daald/ubuntu32:xenial)	8m 12s
pedantic (fedora)	1m 54s
linux-asan-ubsan (ubuntu-latest)	27m 56s
documentation	3m 21s
linux-gcc (ubuntu-20.04)	7m 54s
linux-gcc-default (ubuntu-latest)	10m 16s
linux-leaks (ubuntu-latest)	11m 31s
linux-sha256 (ubuntu-latest)	10m 14s
linux-TEST-vars (ubuntu-20.04)	8m 4s
osx-clang (macos-13)	28m 16s
win+VS test	0s
osx-gcc (macos-13)	31m 11s
sparse	5m 3s
static-analysis	3m 21s
win build	7m 4s
win test (2)	6m 55s
win test (1)	4m 18s
win test (3)	6m 27s
win test (0)	5m 33s
win test (4)	6m 37s
win test (5)	5m 18s
win test (6)	5m 10s
win test (7)	6m 37s
win test (8)	4m 4s
win test (9)	4m 25s
	3h 47m 6s

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