[sil-prespecialization] Whitelist the Swift._allocateUninitializedArray

When pre-specialization was introduced I forgot to whitelist the _allocateUninitializedArray.

As a result, the creation of an array with elements of builtin types was using a generic code. Moreover, due to use of generics, a lot of getGenericMetadata runtime calls were performed, resulting in increased memory usage.

With this change, the memory usage of a "hello, world" Swift-app is down to 5.7KB.

Swift SVN r31322

Author: swiftix

lib/SILPasses/Utils/Generics.cpp

@@ -85,6 +85,7 @@ bool swift::isWhitelistedSpecialization(StringRef SpecName) {
       "_ContiguousArrayBuffer",
       "Range",
       "RangeGenerator",
+      "_allocateUninitializedArray",
       "UTF8",
       "UTF16",
       "String",