extend/ENV/std.rb: Fix libxml2 style error
extend/ENV/std.rb: Fix libxml2 style error

rwhogg/brew,maxim-belkin/brew,maxim-belkin/brew,Linuxbrew/brew,rwhogg/brew,hanxue/linuxbrew,rwhogg/brew,hanxue/linuxbrew,hanxue/linuxbrew,Linuxbrew/brew,Linuxbrew/brew,maxim-belkin/brew,Linuxbrew/brew