cpp: Rename Makefiles under test/cpp

".mk" is the usual extension for makefiles not named
"GNUMakefile", "Makefile", or "makefile".  "Makefile.thrift"
should be a Thrift IDL file (think "Makefile.PL").

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@761480 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/test/cpp/Makefile.stress b/test/cpp/Stress-test.mk
similarity index 100%
rename from test/cpp/Makefile.stress
rename to test/cpp/Stress-test.mk

diff --git a/test/cpp/Makefile.thrift b/test/cpp/Thrift-test.mk
similarity index 100%
rename from test/cpp/Makefile.thrift
rename to test/cpp/Thrift-test.mk