Remove $FreeBSD$: two-line .h pattern

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

fusefs tests: handle -Wdeprecated* issues with GoogleTest 1.14.0

`INSTANTIATE_TEST_CASE_P` has been replaced with `INSTANTIATE_TEST_SUITE_P`.
Replace all uses of the former macro with the latter macro.

While here, address the fact that the latter macro doesn't permit some
of the constructions that the former macro did, e.g., empty parameters,
etc.

MFC after: 2 weeks
Reviewed by: asomers
Differential Revision: https://reviews.freebsd.org/D41398

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

fusefs: use the fsname mount option if set

The daemon can specify fsname=XXX in its mount options. If so, the file
system should report f_mntfromname as XXX during statfs. This will show
up in the output of commands like mount and df.

Submitted by: Ali Abdallah <ali.abdallah@suse.com>
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D35090

fusefs: add a test for the subtype= option

At mount time server can set, for example, "subtype=xfs", so that
mount(8) will later show the mountpoint's file system as "fusefs.xfs".
fusefs has had this feature ever since the original GSoC commit in 2012,
but there's never been a test for it.

MFC after: 2 weeks

fusefs: add SVN Keywords to the test files

Reported by: SVN pre-commit hooks
MFC after: 15 days
MFC-With: r350665
Sponsored by: The FreeBSD Foundation

fusefs: make the tests more cplusplusy

* Prefer std::unique_ptr to raw pointers
* Prefer pass-by-reference to pass-by-pointer
* Prefer static_cast to C-style cast, unless it's too much typing

Reported by: ngie
Sponsored by: The FreeBSD Foundation

fusefs: Allow update mounts

Allow "mount -u" to change some mount options for fusefs.

Sponsored by: The FreeBSD Foundation