glocalfile: Use MAXSYMLINKS when following symlinks

Currently, readlink() is used only 12 times when expanding symlinks.
However, kernel uses 40 for this purpose and it is defined as MAXSYMLINKS.
Use that constant if available, or 40. See:
https://github.com/torvalds/linux/include/linux/namei.h.
9 jobs for <span class="ref-name">wip/oholy/fix-trash-symlink</span> in 15 minutes and 31 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Build
passed #130538
cross-android_api21_arm64

00:07:37

passed #130539
cross-android_api28_arm64

00:07:45

passed #130540
cross-mingw64

00:07:36

passed #130537
fedora-autotools-x86_64

00:12:34

passed #130536
fedora-x86_64

00:14:28

passed #130543
freebsd-11
freebsd-11-x86_64

00:04:24

passed #130541
win32
msys2-mingw32

00:10:21

passed #130542
win32
vs2017-x64

00:07:54

 
  Coverage
passed #130544
coverage

00:01:01

74.9%