fldb: Add -q/--quiet option which can be specified several times

One occurence of the option suppresses the "Ignoring non-file" message,
two or more suppress other warnings like unreadable files and such.

480531b8-ca2e-11e2-9d47-001f3b596ec9
fldb.t: Add four tests for -q/--quiet

d669a0f6-ca2e-11e2-a1bc-001f3b596ec9
Merge branch 'fldb.add-quiet'

Add -q/--quiet option + tests.

* fldb.add-quiet:
  fldb.t: Add four tests for -q/--quiet
  fldb: Add -q/--quiet option which can be specified several times

13b410ae-ca2f-11e2-aa2c-001f3b596ec9