Bug 797316 - New Mauritanian ouguiya MRU not supported

Add new MRU with info from
https://www.currency-iso.org/dam/downloads/lists/list_one.xml

libgnucash/engine/iso-4217-currencies.xml

@@ -1746,6 +1746,19 @@
   smallest-fraction="5"
   local-symbol="UM"
 />
+<!-- "MRU" - "Ouguiya"
+-->
+<currency
+  isocode="MRU"
+  fullname="Ouguiya"
+  unitname="ouguiya"
+  partname="khoum"
+  namespace="ISO4217"
+  exchange-code="929"
+  parts-per-unit="100"
+  smallest-fraction="100"
+  local-symbol="UM"
+/>
 <!-- "MTL" - "Maltese Lira"
   2008-01-01 "EUR" 0.4293
 -->