core: added LGTM analysis config file

- LGTM is integrated by github

.lgtm.yml

@@ -0,0 +1,29 @@
+extraction:
+  cpp:
+    prepare:
+      packages:
+      - "bison"
+      - "default-libmysqlclient-dev"
+      - "flex"
+      - "libcurl4-openssl-dev"
+      - "libjansson-dev"
+      - "libhiredis-dev"
+      - "liblua5.1-0-dev"
+      - "libpcre3-dev"
+      - "libncurses5-dev"
+      - "libpq-dev"
+      - "libreadline-dev"
+      - "libssl-dev"
+      - "libunistring-dev"
+      - "libxml2-dev"
+      - "pkg-config"
+      - "python3"
+      - "python3-dev"
+      - "uuid-dev"
+      - "zlib1g-dev"
+    after_prepare:
+    - "export PKG_CONFIG_PATH=$LGTM_WORKSPACE/usr/lib/pkgconfig:$PKG_CONFIG_PATH"
+    configure:
+      command: "make include_modules='app_lua app_python3 db_mysql db_postgres db_redis dialplan http_client jansson lcr ndb_redis presence presence_xml presence_dialoginfo pua pua_dialoginfo topos_redis uuid websocket xmlops' cfg"
+    index:
+      build_command: "make all"