Added instruction to use TScanCode [#CLICKHOUSE-2].

dbms/tests/instructions/tscancode.txt

@@ -0,0 +1,26 @@
+# TScanCode is a static analyzer from Tencent
+# It looks like to be based on CppCheck
+
+git clone git@github.com:Tencent/TscanCode.git
+cd TscanCode/trunk
+make -j4
+
+# It looks weird that TScanCode itself compiles with multiple warnings like 'unused-but-set-variable' and 'misleading-indentation'
+
+# Run analysis:
+
+./tscancode -j4 --enable=all ~/work/ClickHouse 2> result.txt
+
+# It has no way to remove specific directories. We have to checkout ClickHouse to separate directory and manually remove "contrib".
+# Otherwise it segfaults when analysing llvm submodule.
+
+# It works quite fast:
+
+real    0m17.174s
+user    0m45.498s
+sys     0m0.496s
+
+wc -l result.txt
+61 result.txt
+
+# It gives almost all false positives.