xbps-src: multiple improvements to messages and phases.

- Prefix all messages with 'Package 'pkgname (version)': ..." to really
  understand what's going on. Add more messages in some stages...
- Do not run pre/post_{configure,build,install} or do_{build,install} stages
  if they were executed successfully in the past.

xbps-src/shutils/extract_funcs.sh

@@ -71,7 +71,7 @@ extract_distfiles()
 		mkdir -p ${wrksrc} || return 1
 	fi
 
-	msg_normal "Extracting $pkgname-$lver distfile(s)."
+	msg_normal "Package '$pkgname ($lver)': extracting distfile(s), please wait..."
 
 	for f in ${distfiles}; do
 		curfile=$(basename $f)