LLVM: fix ABI size of optional and error union types

Previously, the Zig ABI size and LLVM ABI size of these types disagreed
sometimes. This code also corrects the logging messages to not trigger
LLVM assertions.

src/codegen/llvm/bindings.zig

@@ -304,6 +304,9 @@ pub const Type = opaque {
 
     pub const isOpaqueStruct = LLVMIsOpaqueStruct;
     extern fn LLVMIsOpaqueStruct(StructTy: *const Type) Bool;
+
+    pub const isSized = LLVMTypeIsSized;
+    extern fn LLVMTypeIsSized(Ty: *const Type) Bool;
 };
 
 pub const Module = opaque {