std.cfg: Add support for std::map::count() (#1655)

Reference: https://en.cppreference.com/w/cpp/container/map/count

Author: versat

cfg/std.cfg

@@ -6165,6 +6165,17 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
     <returnValue type="std::size_t"/>
     <noreturn>false</noreturn>
   </function>
+  <!-- size_type std::map::count( const Key& key ) const; -->
+  <!-- template< class K > size_type std::map::count( const K& x ) const; // since C++14 -->
+  <function name="std::map::count">
+    <noreturn>false</noreturn>
+    <returnValue type="size_t"/>
+    <use-retval/>
+    <const/>
+    <arg nr="1">
+      <not-uninit/>
+    </arg>
+  </function>
   <function name="std::list::back,std::list::front,std::forward_list::front,std::queue::back,std::queue::front,std::vector::back,std::vector::front,std::array::front,std::array::back">
     <use-retval/>
     <noreturn>false</noreturn>