whereis: cleanup debug stuff, fix argv[] usage

* use debug stuff from include/debug.h and make whereis(1) sensitive
  to WHEREIS_DEBUG=0xffff mask

* fix problem with argv[] usage

  # whereis -b -m -M /usr/share/man/man1 -B /usr/bin -f gcc
  bin: /usr/local/bin
  gcc: /usr/bin/gcc /usr/lib/gcc /usr/libexec/gcc /usr/share/man/man1/gcc.1.gz

the code ignores "-B" and /usr/bin is interpreted as search pattern,
expected result is:

  # whereis -b -m -M /usr/share/man/man1 -B /usr/bin -f gcc
  gcc: /usr/share/man/man1/gcc.1.gz /usr/bin/gcc

Addresses: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=765306
Signed-off-by: Karel Zak <kzak@redhat.com>
whereis: reset search mask more carefully

 # whereis -m cal -M /usr/share/man/man1/ -f ls
 cal: /usr/share/man/man1/cal.1.gz /usr/share/man/man1p/cal.1p.gz
 ls: /usr/bin/ls /usr/share/man/man1/ls.1.gz

the -M also resets the search mask, so for 'ls' it returns also
binaries. That's bug. Expected result is:

 # ./whereis -m cal -M /usr/share/man/man1/ -f ls
 cal: /usr/share/man/man1/cal.1.gz /usr/share/man/man1p/cal.1p.gz
 ls: /usr/share/man/man1/ls.1.gz

the search mask has to be sensitive only to -b -m -s options,
otherwise the semantic is pretty messy.

Signed-off-by: Karel Zak <kzak@redhat.com>