scripted-diff: Small locking rename

Call sync.h primitives "locks" and "mutexes" instead of "blocks" and "waitable
critical sections" to match current coding conventions and c++11 standard
names.

This PR does not rename the "CCriticalSection" class (though this could be done
as a followup) because it is used everywhere and would swamp the other changes
in this PR. Plain mutexes should mostly be preferred instead of recursive
mutexes in new code anyway.

-BEGIN VERIFY SCRIPT-
set -x
set -e
ren() { git grep -l $1 | xargs sed -i s/$1/$2/; }
ren CCriticalBlock           UniqueLock
ren CWaitableCriticalSection Mutex
ren CConditionVariable       std::condition_variable
ren cs_GenesisWait           g_genesis_wait_mutex
ren condvar_GenesisWait      g_genesis_wait_cv
perl -0777 -pi -e 's/.*typedef.*condition_variable.*\n\n?//g' src/sync.h
-END VERIFY SCRIPT-

src/validation.h

@@ -151,8 +151,8 @@ extern BlockMap& mapBlockIndex;
 extern uint64_t nLastBlockTx;
 extern uint64_t nLastBlockWeight;
 extern const std::string strMessageMagic;
-extern CWaitableCriticalSection g_best_block_mutex;
-extern CConditionVariable g_best_block_cv;
+extern Mutex g_best_block_mutex;
+extern std::condition_variable g_best_block_cv;
 extern uint256 g_best_block;
 extern std::atomic_bool fImporting;
 extern std::atomic_bool fReindex;