Reduce number of packages install_prereq installs on Debian systems.

'search' will look for any package containing the name provided, so we need to
force a more exact search.
........

Merged revisions 379276 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@379277 65c4cc65-6c06-0410-ace0-fbb531ad65f3

contrib/scripts/install_prereq

@@ -50,8 +50,12 @@ in_test_mode() {
 }
 
 check_installed_debs() {
-	aptitude -F '%c %p' search "$@" 2>/dev/null \
-	| awk '/^p/{print $2}'
+	for pack in "$@"
+	do
+		tocheck="${tocheck} ^${pack}$"
+	done
+	aptitude -F '%c %p' search ${tocheck} 2>/dev/null \
+ 	| awk '/^p/{print $2}'
 }
 
 # parsing the output of yum is close to impossible.