Improved pkg best matching in rpool, and support for exact pkgver matches.

- xbps_repository_pool_find_pkg in best match case, now returns the
  newest package version available in rpool.
- Added xbps_repository_pool_find_pkg_exact that returns a package
  by exact matching a pkgver.
- Removed xbps_handle_alloc(), the user is free to use memory
  allocated from heap or stack.
- Improved API documentation in preparation for 0.12.

Bumped XBPS_API_VERSION again.

lib/initend.c

@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2011 Juan Romero Pardines.
+ * Copyright (c) 2011-2012 Juan Romero Pardines.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -205,8 +205,6 @@ xbps_end(struct xbps_handle *xh)
 	if (xh->cachedir_priv != NULL)
 		free(xh->cachedir_priv);
 
-	free(xh);
-	xh = NULL;
 	xhp = NULL;
 }
 
@@ -217,12 +215,6 @@ xbps_handle_get(void)
 	return xhp;
 }
 
-struct xbps_handle *
-xbps_handle_alloc(void)
-{
-	return calloc(1, sizeof(struct xbps_handle));
-}
-
 static void
 common_printf(FILE *f, const char *msg, const char *fmt, va_list ap)
 {