Provide fixes for the recently added Array.uniq! test cases.

src/classes/Array.pir

@@ -270,9 +270,23 @@ Return a sorted copy of the list
 .end
 
 .sub 'uniq!' :method
+    .param pmc block :optional :named("!BLOCK")
+    .param int block_flag :opt_flag
+    if block_flag goto with_block
     $P0 = self.'uniq'()
+    goto done
+  with_block:
+    $P0 = self.'uniq'(block :named("!BLOCK"))
+  done:
+    $I0 = elements $P0
+    $I1 = elements self
+    if $I0 == $I1 goto no_change
     self = 0
     self.'concat'($P0)
+    .return (self)
+  no_change:
+    $P0 = get_hll_global 'nil'
+    .return ($P0)
 .end
 
 .sub reject :method

t/array/uniq.t

@@ -22,15 +22,11 @@ c = [3,13,2,25,5,9]
 c = c.uniq {|x| x % 10}
 is c, [3,2,25,9], "uniq with block"
 
-todo "Array#uniq! with block"
-# The call to uniq! with a block fails.
-# This is wrong because in Ruby every method will work when a block is passed, even when it is ignored.
-d = [3,13,2,25,5,9]
-#d = c.uniq! {|x| x % 10}
+c = [3,13,2,25,5,9]
+d = c.uniq! {|x| x % 10}
 is d, [3,2,25,9], "uniq! with block"
 
 # uniq! returns nil when nothing is changed
-todo "Array#uniq! where nothing is changed should return nil"
 e = [4, 5, 6]
 e = e.uniq!
 is e, nil, "uniq! removing nothing"