Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

rtld-elf: Remove _PATH_ELF32_HINTS and _COMPAT32_PATH_RTLD

These are no longer referenced, with the one user of each now using the
double-underscore version with "32" as an argument instead.

Reviewed by: kib, brooks, jhb
Differential Revision: https://reviews.freebsd.org/D40935

rtld-elf: Migrate from COMPAT_32BIT to generic COMPAT_libcompat/LIBCOMPAT

We still have a tiny amount of libcompat-specific code in rtld_paths.h,
but it's been deduplicated as much as possible, and in future we may
wish to just push these variables down to the few consumers of them and
make them use the double-underscore variants with a libcompat argument
rather than give them names here.

See commit 8fad2cda93c7 ("bsd.compat.mk: Provide new CPP and sub-make
variables") for the context behind this change.

Reviewed by: kib, brooks, jhb
Differential Revision: https://reviews.freebsd.org/D40925

libcasper: Move helper libraries from /lib/casper to /lib.

These libraries are linked to directly by applications rather than
opened at runtime via dlopen().

Discussed with: oshogbo
Reviewed by: markj, emaste
Differential Revision: https://reviews.freebsd.org/D39245

rtld: add support for the $LIB token

similar to the same token in glibc.

Requested and reviewed by: bapt
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D37329

rtld-elf: Remove libsoft support

Remove support for loading libsoft libraries.

Sponsored by: Netflix

rtld_paths.h: Provide _PATH_ELF32_HINTS string, unconditionally

Reviewed by: emaste
Tested by: jbeich
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D33058

rtld-elf/paths.h: Make it usable outside rtld

but still for tightly coupled things like ldd(1)

Rename paths.h to rtld_paths.h.
Add guard for rtld-specific externs declarations.
Add _COMPAT32_BASENAME_RTLD and _COMPAT32_PATH_RTLD.

Reviewed by: arichardson, jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D32464