FEATURES=case-insensitive-fs for bug #524236

When case-insensitive-fs is enabled in FEATURES, the dblink.isowner
method and the _owners_db class will be case-insensitive. This causes
the collision-protect and unmerge code to behave correctly for a
case-insensitive file system. If the file system is case-insensitive
but case-preserving, then case is preserved in the CONTENTS data of
installed packages.

X-Gentoo-Bug: 524236
X-Gentoo-Url: https://bugs.gentoo.org/show_bug.cgi?id=524236