MFC r256533:
Unhide "Serial Number" lines from bootverbose.  That information may
be useful for system administration to have in hard copy (in logs) if
one of several devices suddenly dies.
MFC r256552:
Unify periph invalidation and destruction reporting.
Print message containing device model and serial number on invalidation.
MFC r256842:

  Fix 'make delete-old-libs' and 'make check-libs' to delete .debug
  files created by WITH_DEBUG_FILES. Also cleanup .symbols files from
  the period between r244236 when .symbols were supported and r251512
  when they were renamed to .debug.

  Only propose to delete a .debug file if the corresponding library
  itself was deleted already.

Approved by:	bapt