Control mutex kind based on build settings

Use PTHREAD_MUTEX_ERRORCHECK_NP if '-g -O0', PTHREAD_MUTEX_DEFAULT otherwise

Signed-off-by: Shachar Sharon <shachars@xxxxxx>
Tuned shutdown process: destage as much dirty as you can

Control log-debug via pseudo-fs
Account and export metadata elements via pseudo-fs

Meta files:
  $ cat .funex/super/vstats
  $ cat .funex/super/iostat
  ...

Signed-off-by: Shachar Sharon <shachars@xxxxxx>
Query fs-internals via sub-command: 'inquiry'

Using pseudo-fs to export file-system internals; using 'inquiry' subcmd
to read the relevant files in pseudo-fs. Placed names-defs in dedicated
header 'names.h'.

Signed-off-by: Shachar Sharon <shachars@xxxxxx>
Added global-fs blocks accounting (statvfs)
gbx: Test 'statvfs(3p)' system call
Changed sub-command name to 'stats' (was: 'inquery')

Probe file-system's stats via pseudo-fs, probe inode via 'fquery' ioctl
gbx: Test 'ftruncate(3p)' system call (basic tests)