Add flag qualifying field to be indexed exclusively with prefix

src/sampleconf/fields

@@ -29,6 +29,10 @@
 # (NOT CURRENTLY IMPLEMENTED) would automatically boost the weight of a
 # caption-based field query (ie: caption:mytitle or title:mytitle) at query
 # time.
+#
+# The pfxonly attribute can also be set on entries to express that terms
+# from the field should be indexed only with a prefix (in general, field
+# terms are indexed both with and without a prefix).
 
 # The following ones are probably hard-coded in the c code, can't change at
 # all.
@@ -46,6 +50,7 @@ abstract = XS
 filename = XSFN
 rclUnsplitFN = XSFS
 xapyear = Y
+recipient = XTO
 
 # Extension examples. These are actually used by default by Recoll, you can
 # add your own to search for fields produced by the filters and not handled
@@ -57,7 +62,6 @@ xapyear = Y
 # I hereby commit to not using XY for Recoll:
 # *** USE XY for beginning your local prefixes *** ie:
 # myfield = XYMYPREF
-recipient = XTO
 
 [stored]
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