Add support for using "pkg+http://" for the PACKAGESITE.

pkg 1.2 is adding this support as well. This should help
lessen the confusion on why the default SRV PACKAGESITE
does not load in a browser.

Adapated from:	matthew's upstream pkg change
Approved by:	bapt
MFC after:	2 days

usr.sbin/pkg/config.c

@@ -62,7 +62,7 @@ static struct config_entry c[] = {
 	[PACKAGESITE] = {
 		PKG_CONFIG_STRING,
 		"PACKAGESITE",
-		"http://pkg.FreeBSD.org/${ABI}/latest",
+		URL_SCHEME_PREFIX "http://pkg.FreeBSD.org/${ABI}/latest",
 		NULL,
 		false,
 	},

usr.sbin/pkg/config.h

@@ -30,6 +30,7 @@
 #define _PKG_CONFIG_H
 
 #define _LOCALBASE "/usr/local"
+#define URL_SCHEME_PREFIX "pkg+"
 
 typedef enum {
 	PACKAGESITE = 0,

usr.sbin/pkg/pkg.c

@@ -168,6 +168,13 @@ bootstrap_pkg(void)
 		warnx("No MIRROR_TYPE defined");
 		return (-1);
 	}
+
+	/* Support pkg+http:// for PACKAGESITE which is the new format
+	   in 1.2 to avoid confusion on why http://pkg.FreeBSD.org has
+	   no A record. */
+	if (strncmp(URL_SCHEME_PREFIX, packagesite,
+	    strlen(URL_SCHEME_PREFIX)) == 0)
+		packagesite += strlen(URL_SCHEME_PREFIX);
 	snprintf(url, MAXPATHLEN, "%s/Latest/pkg.txz", packagesite);
 
 	snprintf(tmppkg, MAXPATHLEN, "%s/pkg.txz.XXXXXX",