idr: Remove non-standard function idr_init1()

It never was part of the Linux idr API.
idr: Mark non-public functions as static

Remove idr_alloc()'s prototype, there was no function body
man(1): import man(1) replacement

Vanilla sources; not yet hooked up to the build.

Taken-from: NetBSD
man(1): fix build and adapt for DragonFly

swildner suggested to get rid of the cat* magic, so let's try this out
for mandoc(1).  Still not hooked up to the build, but ready for testing.
Don't forget to manually install etc/man.conf to your system.
man(1): tweak literal file interpretation

The previous behaviour would not catch the following invoke:

    # man usr.bin/man/man.1

Now, as a generalised rule, the literal interpretation is triggered by
any '/' character in the requested page(s).
man(1): fixup literal file suffix parsing

Look for last slash and assume next dot is the suffix start.  Fixes
display of compressed pages as configured via man.conf(5), e.g.

    # man ./man.1.gz