Add xsl:map/@select

[michaelhkay]

I was surprised to discover that the xsl:map instruction does not allow a select attribute.

For many use cases it might make the instruction equivalent to xsl:sequence:

<xsl:map select="map:build(.....)"/>

<xsl:map select="{'a': 1, 'b': 2}"/>

but it still has documentary value; and there are other cases where it's not merely cosmetic:

<xsl:map select="$map1, $map2 => map:remove('extra'), {'extra': 17}"/>

There's no change to the semantics, the value of the select attribute is handled just like the value of the sequence constructor.