lapi/mount.h: Document reason for not including <linux/mount.h> #341

Job	Run time
job (debian:stable, gcc, i386)	11m 13s
job (debian:stable, ppc64el, powerpc64le-linux-gnu-gcc, 1, out, cross-compile)	4m 56s
job (debian:stable, arm64, aarch64-linux-gnu-gcc, 1, out, cross-compile)	5m 5s
job (debian:stable, s390x, s390x-linux-gnu-gcc, 1, out, cross-compile)	4m 55s
job (alpine:latest, gcc, asciidoctor)	10m 5s
job (debian:stable, gcc, out, minimal)	8m 6s
job (opensuse/archive:42.2, gcc)	8m 17s
job (quay.io/centos/centos:stream9, gcc, asciidoc-pdf, out)	8m 46s
job (debian:testing, gcc, asciidoctor-pdf)	11m 27s
job (debian:oldstable, clang)	11m 51s
job (fedora:latest, clang, 1, asciidoctor-pdf)	9m 14s
job (opensuse/leap:latest, gcc, asciidoc-pdf)	9m 19s
job (debian:oldstable, gcc, asciidoctor)	10m 37s
job (debian:testing, clang, asciidoctor-pdf)	11m 48s
job (ubuntu:jammy, gcc, asciidoctor, out)	5m 47s
job (ubuntu:bionic, gcc, asciidoc-pdf)	10m 5s
	2h 21m 31s

Provide feedback