Fix connection count query for mariadb

Author: GromNaN

src/Illuminate/Database/Schema/Grammars/MariaDbGrammar.php

@@ -55,4 +55,9 @@ protected function typeGeometry(Fluent $column)
             $column->srid ? ' ref_system_id='.$column->srid : ''
         );
     }
+
+    public function compileConnectionCount()
+    {
+        return 'select variable_value as `Value` from information_schema.global_status where variable_name = \'Threads_connected\'';
+    }
 }

src/Illuminate/Database/Schema/Grammars/MySqlGrammar.php

@@ -1340,6 +1340,6 @@ protected function wrapJsonSelector($value)
 
     public function compileConnectionCount()
     {
-        return 'select variable_value as `Value` from performance_schema.session_status where variable_name = "threads_connected"';
+        return 'select variable_value as `Value` from performance_schema.session_status where variable_name = \'threads_connected\'';
     }
 }

src/Illuminate/Database/Schema/Grammars/SqlServerGrammar.php

@@ -1057,6 +1057,6 @@ public function quoteString($value)
 
     public function compileConnectionCount()
     {
-        return 'select count(*) Value from sys.dm_exec_sessions where status = "running"';
+        return 'select count(*) Value from sys.dm_exec_sessions where status = N\'running\'';
     }
 }