[Import as Member] Inferred inits are factory

Inferred inits from C via import-as-member are factory inits, so treat
them as such. Core Graphics test case included.

Author: milseman

lib/ClangImporter/ClangImporter.cpp

@@ -2564,6 +2564,11 @@ auto ClangImporter::Implementation::importFullName(
       else if (inference.isSetter())
         result.AccessorKind = ImportedAccessorKind::PropertySetter;
 
+      // Inits are factory. These C functions are neither convenience nor
+      // designated, as they return a fully formed object of that type.
+      if (inference.isInit())
+        result.InitKind = CtorInitializerKind::Factory;
+
       return result;
     }
   }

test/ClangModules/CoreGraphics_test.swift

@@ -87,6 +87,15 @@ public func testColorRenames(color: CGColor,
 // CHECK:   ret void
 }
 
+// Test factory-ness of inferred imports
+extension CGMutablePath {
+  // CHECK-LABEL: define %{{.*}}CGMutablePath* {{.*}}CGMutablePath{{.*}}(i1{{.*}})
+  public convenience init(p: Bool) {
+    self.init()
+    // CHECK: tail call %struct.CGPath* @CGPathCreateMutable()
+  }
+}
+
 // CHECK-LABEL: define void {{.*}}testRenames{{.*}} {
 public func testRenames(transform: CGAffineTransform, context: CGContext,
                         point: CGPoint, size: CGSize, rect: CGRect,