Mega-commit with improvements and changes done in the past days.

- Introduce package states: unpacked, broken, installed, etc.
  Not yet finished, only unpacked and installed are used for now.

- Move package metadata files in binary packages directly to
  the top directory, this speeds up some ops and makes easier to
  continue working in future changes.

- xbps-bin: -C flag to check the hash of package files has been
  superseded by the 'check' target, which verifies the integrity
  of an installed package.

- Use the 'essential' object when upgrading packages, overwritting
  current files. This is needed for critical packages like sh, libc
  and others.

- Miscellaneous tweaks and improvements thorough the code.

--HG--
extra : convert_revision : 2073fcc123efc24b3e9327b5e22aa91752f20df6

bin/xbps-bin/Makefile

@@ -1,5 +1,5 @@
 BIN	= xbps-bin
-OBJS	= install.o main.o remove.o ../xbps-repo/util.o
+OBJS	= check.o install.o main.o remove.o ../xbps-repo/util.o
 
 TOPDIR = ../..
 include $(TOPDIR)/prog.mk