Generate C interop adapters for functions defined in headers

Interop/Indexer/src/main/kotlin/org/jetbrains/kotlin/native/interop/indexer/Indexer.kt

@@ -266,7 +266,10 @@ internal class NativeIndexImpl(val language: Language) : NativeIndex() {
                     Language.C -> clang_Cursor_getMangling(cursor).convertAndDispose()
                 }
 
-                functionByName[name] = FunctionDecl(name, args, returnType, binaryName)
+                val definitionCursor = clang_getCursorDefinition(cursor)
+                val isDefined = (clang_Cursor_isNull(definitionCursor) == 0)
+
+                functionByName[name] = FunctionDecl(name, args, returnType, binaryName, isDefined)
             }
 
             CXIdxEntity_Enum -> {

Interop/Indexer/src/main/kotlin/org/jetbrains/kotlin/native/interop/indexer/NativeIndex.kt

@@ -69,7 +69,8 @@ class Parameter(val name: String?, val type: Type)
 /**
  * C function declaration.
  */
-class FunctionDecl(val name: String, val parameters: List<Parameter>, val returnType: Type, val binaryName: String)
+class FunctionDecl(val name: String, val parameters: List<Parameter>, val returnType: Type, val binaryName: String,
+                   val isDefined: Boolean)
 
 /**
  * C typedef definition.

Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/StubGenerator.kt

@@ -909,7 +909,8 @@ class StubGenerator(
             return true
         }
 
-        return this.returnsRecord() ||
+        return this.isDefined ||
+                this.returnsRecord() ||
                 this.parameters.map { it.type }.any { it.unwrapTypedefs() is RecordType }
     }