case insensitive attribute mapping

[BitPatty]

Fixes an issue ( see #900 and #974 ) where attributes with uppercase characters would be filtered out in the response due to the lowercase matching in the search response:

node-ldapjs/lib/messages/search_response.js

Lines 57 to 71 in b86c493

	Object.keys(entry.attributes).forEach(function (a) {
	const _a = a.toLowerCase()
	if (!nofiltering && _a.length && _a[0] === '_') {
	savedAttrs[a] = entry.attributes[a]
	delete entry.attributes[a]
	} else if (!nofiltering && self.notAttributes.indexOf(_a) !== -1) {
	savedAttrs[a] = entry.attributes[a]
	delete entry.attributes[a]
	} else if (all) {
	// do nothing
	} else if (self.attributes.length && self.attributes.indexOf(_a) === -1) {
	savedAttrs[a] = entry.attributes[a]
	delete entry.attributes[a]
	}
	})