swedish: Remove -et or -en when stem ends in et

Removing -et and -en in general is problematic, as many words end in -et
or -en where this isn't a suffix, but very few end in -etet or -eten
where the last two letters aren't a suffix (and those that do don't seem
to suffer if we make the stem not have the -et).

Fixes #47

algorithms/swedish.sbl

@@ -1,5 +1,6 @@
 routines (
            mark_regions
+           R1
            main_suffix
            consonant_pair
            other_suffix
@@ -33,6 +34,8 @@ define mark_regions as (
 
 backwardmode (
 
+    define R1 as $p1 <= cursor
+
     define main_suffix as (
         setlimit tomark p1 for ([substring])
         among(
@@ -66,6 +69,7 @@ define stem as (
     do mark_regions
     backwards (
         do main_suffix
+        do ( ['et' or 'en'  R1 ] 'et' delete )
         do consonant_pair
         do other_suffix
     )