installer: pkg.c (HEAD) pkg.h (HEAD)

[mis]

Module name:	installer
Changes by:	mis	03/01/21 02:15:36

Modified files:
	pkg.c pkg.h

Log message:
- "arch" and "os" moved to global dictionary (saves about 10 bytes memory
   per packege)
- added NVR member and coresponding cmp* functions;
  simplifies "poldek --shell"-like apps