Added support for a cachedir to store downloaded binpkgs.

libxbps:
 * Added xbps_set_cachedir() and xbps_get_cachedir(). By default it's
   set to /var/cache/xbps if not specified and it's always relative
   to the root directory.
 * Move mkpath() code from sync_remote_pkgidc.c into its own file mkpath.c
   to use it in another parts of the code.
 * Added xbps_get_binpkg_local_path(), that returns the local path to
   a binary package file, stored in cachedir or local repo.
 * Remote pkg index files are now stored directly in metadir/repodir,
   skipping the arch directory because binpkgs are now in cachedir.

xbps-bin:
 * Added -c flag to set the cachedir.
 * Check sha256 hashes in the download stage so that it can check
   a downloaded binpkg immediately once is stored.
 * If a binpkg doesn't match the hash it will be refetched.

Bump XBPS_RELVER to 20091128.

--HG--
extra : convert_revision : xtraeme%40gmail.com-20091128013841-kkcvk07lsqdr26w8

bin/xbps-bin/main.c

@@ -58,12 +58,12 @@ usage(void)
 	"    show-revdeps\t<pkgname>\n"
 	"    update\t\t<pkgname>\n"
 	" Options shared by all targets:\n"
+	"    -c\t\t<cachedir>\n"
 	"    -r\t\t<rootdir>\n"
 	"    -v\t\tShows verbose messages\n"
 	"    -V\t\tPrints the xbps release version\n"
 	" Options used by the (auto)remove and install target:\n"
-	"    -f\t\tForce installation or removal of packages.\n"
-	"      \t\tBeware with this option if you use autoremove!\n"
+	"    -f\t\tBypasses the questions.\n"
 	"\n");
 	exit(EXIT_FAILURE);
 }
@@ -116,8 +116,11 @@ main(int argc, char **argv)
 
 	force = verbose = false;
 
-	while ((c = getopt(argc, argv, "CVfr:v")) != -1) {
+	while ((c = getopt(argc, argv, "Vcfr:v")) != -1) {
 		switch (c) {
+		case 'c':
+			xbps_set_cachedir(optarg);
+			break;
 		case 'f':
 			flags |= XBPS_FLAG_FORCE;
 			force = true;