This continues 6ab95220 (t/qemu-runlinux: Issue terminal resize before
running program) and fully initializes terminal before spawning user
application.

This has practical effect to restore line wrapping for xterm, as kernel,
initially assuming it has "linux" type terminal, somehow messes xterm
settings: before the patch lines that were wider than terminal width were
not wrapped and characters in the last position were printed over each
other. After the patch printed lines are automatically wrapped and test
output is not lost.

Tput hint found here:

	https://unix.stackexchange.com/questions/105958

	0: ERROR+ on boot/run
	1: INFO+  on      run
	2: INFO+  on boot/run
	3: DEBUG+ on boot/run

It is convenient not to see large kernel boot log on every test run. "1"
(single -v) is also convenient: one can skip the boot log but still see
details of what is going on when test workload is run. -vv and -vvv are
there to see full picture.

bpf is needed for tools like bpftrace.
fusectl is needed to observe things like /sys/fs/fuse/connections/X/waiting.

Else program inside sees default terminal settings to be 80x25,
while after the patch it sees correct settings.

Still something is not completely right with terminal settings, as e.g.
vsplit is not working correctly in vim (vertical ruler is not straight).

Graphics mode runs in another window with its own terminal emulation,
so propagating e.g. TERM=xterm to where it is emulated as TERM=linux is
not correct.

Continuing 76d8f76d (Script to run compiled linux kernel with root fs
mounted from host) update the script to run/debug linux inside QEMU:

- teach it to run specified program + args, instead of hardcoded /bin/sh;
- before tailing to user program, builtin init mounts /proc, /sys, ...
  inside - previously it was /proc, /sys from host seen on those
  mountpoints and it was very misleading - e.g. ps was showing processes
  from host, not inside, etc.
- builtin init also cares to run specified program with the same current
  directory that was current on host, and environments such as $HOME,
  $PATH, $TERM, ... are also propagated.
- allow to optionally run QEMU with graphics, instead of stdout only;
- increase available RAM from 128M to 512M (with 128M running py.test
  inside is failing with fork: not enough memory).

This updated version was useful to debug WCFS(*) & FUSE issues by running

	kirr@deco:~/src/wendelin/wendelin.core/wcfs$ ../t/qemu-runlinux ~/src/linux/linux/arch/x86_64/boot/bzImage py.test -vsx -k test_wcfs

See https://marc.info/?l=linux-fsdevel&m=155000277921155&w=2 for details.

(*) WCFS is still being draft and worked on t branch.

Useful to debug (via either printk or gdb) the kernel - one can boot it,
and tweak compile test program on host and be ready to test it inside
qemu on tested kernel. Another use case is to add tracing printk to
kernel and to boot it on each iteration. Booting via qemu means the
workflow is not disrupted as would with rebooting the hardware.

With this tool it was straightforward to find out why mmap-alias through
mremap does not work for huge pages:

static struct vm_area_struct *vma_to_resize(unsigned long addr,
        unsigned long old_len, unsigned long new_len, unsigned long *p)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma = find_vma(mm, addr);

        if (!vma || vma->vm_start > addr)
                goto Efault;

        if (is_vm_hugetlb_page(vma))            <--
                goto Einval;

mremap_to(...)
{
        /* lots of checks, then */
        vma_to_resize(...)