Attached patch contains some automake cleanups against trunk.
List of small improvements/fixes which my patch delivers:

1. replace @FOO@ by $(FOO) to allow on execute make command override some variables
2. put in each *_SOURCE list all files in separated lines and sort list of those files alphabetically
3. do not use $(top_sourcedir) in paths of static libraries. It should be always used $(top_builddir) to allow build zabbix code from read only source tree
4. remove from src/libs/zbxsysinfo/Makefile.am EXTRA_DIST files which are included in *_SOURCES in subdirectories