catch up with api and system changes in libpcp. added c++ buffer class as well

tests/unittests.cfg

@@ -187,11 +187,10 @@ temporarily disabled
   expect = /HELLO/
 </test>
 
-
 #
 # check usage of unencrypted secret key
 <test check-crypto-unencrypted-secret>
-  cmd = (echo dau; echo foo; echo yes) | $pcp -V vcl -k -x ""
+  cmd = (echo dau; echo foo; echo yes) | $pcp -V vcl -k -x "n/a"
   expect = /added to/
 </test>
 
@@ -489,3 +488,8 @@ disabled, need to re-design invalidkeys.c in order to catch up with new format
   cmd = ./cpptest 3
   expect = /ok/
 </test>
+
+<test check-buffer>
+  cmd = ./cpptest 4
+  expect = /ok/
+</test>