Code clean-up for meson-based build infrastructure.
* es/meson-cleanup:
meson: only check for missing networking syms on non-Windows; add compat impls
meson: fix typo in function check that prevented checking for hstrerror
meson: add a couple missing networking dependencies
meson: do a full usage-based compile check for sysinfo
meson: check for getpagesize before using it
meson: simplify and parameterize various standard function checks