std.xml1 build failure with DMD2.059

[Richard Webb]

std.xml1.d fails to compile with DMD2.059 due to changes to the signature of Object.toHash() (marking as nothrow and such):

std\xml1.d(234): Error: hash is not nothrow
std\xml1.d(232): Error: function std.xml1.Document.toHash 'toHash' is nothrow yet may throw
std\xml1.d(547): Error: this.tag.toHash is not nothrow
std\xml1.d(549): Error: this.items.toConstArray is not nothrow
std\xml1.d(540): Error: function std.xml1.Element.toHash 'toHash' is nothrow yet may throw
std\xml1.d(983): Error: hash is not nothrow
std\xml1.d(981): Error: function std.xml1.Comment.toHash 'toHash' is nothrow yet may throw
std\xml1.d(1065): Error: hash is not nothrow
std\xml1.d(1063): Error: function std.xml1.CData.toHash 'toHash' is nothrow yet may throw
std\xml1.d(1149): Error: hash is not nothrow
std\xml1.d(1147): Error: function std.xml1.Text.toHash 'toHash' is nothrow yet may throw
std\xml1.d(1246): Error: hash is not nothrow
std\xml1.d(1244): Error: function std.xml1.XMLInstruction.toHash 'toHash' is nothrow yet may throw
std\xml1.d(1328): Error: hash is not nothrow
std\xml1.d(1326): Error: function std.xml1.ProcessingInstruction.toHash 'toHash' is nothrow yet may throw

[michaelrynn (michael-rynn-500)]

Change to conform.