The old value was probably fine back in 1998, when that code was imported
(although the comments still mention VAX, which was quite obsolete by then);
now, however, it's too small to handle our libc, which results in some
additional calls to munmap/mmap later on. Asking for more virtual address
space is virtually free, and syscalls are not, thus the change.
It was suggested by kib@ that this might be a symptom of a deeper problem.
It doesn't only affect libc, though - the change also improves rtld memory
management for eg KDE libraries. I guess it's just a natural bloat.
MFC after: 2 weeks
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D12834
ef4968d9e7