Convert constant_time_test and refcount_test to C++.

No source changes, just a rename.

Change-Id: Iaef406d2a04dc8c68c94eb2a98eec6378eaeab66
Reviewed-on: https://boringssl-review.googlesource.com/12975
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/CMakeLists.txt b/crypto/CMakeLists.txt
index fceef1a..97fea5f 100644
--- a/crypto/CMakeLists.txt
+++ b/crypto/CMakeLists.txt
@@ -180,7 +180,7 @@
 add_executable(
   constant_time_test
 
-  constant_time_test.c
+  constant_time_test.cc
 
   $<TARGET_OBJECTS:test_support>
 )
@@ -202,7 +202,7 @@
 add_executable(
   refcount_test
 
-  refcount_test.c
+  refcount_test.cc
 )
 
 target_link_libraries(refcount_test crypto)
diff --git a/crypto/constant_time_test.c b/crypto/constant_time_test.cc
similarity index 100%
rename from crypto/constant_time_test.c
rename to crypto/constant_time_test.cc
diff --git a/crypto/refcount_test.c b/crypto/refcount_test.cc
similarity index 100%
rename from crypto/refcount_test.c
rename to crypto/refcount_test.cc