Use imaginary_part' instead of imaginary' to fix build on Solaris 2.10.

THANKS

@@ -28,6 +28,7 @@ For fixes or providing information which led to a fix:
         Stephen Compall
           Brian Crowder
     Christopher Cramer
+          David Diffenbaugh
           Hyper Division
       Alexandre Duret-Lutz
            Nils Durner
@@ -50,6 +51,7 @@ For fixes or providing information which led to a fix:
           Steve Juranich
         Richard Kim
           Bruce Korb
+           René Köcher
        Matthias Köppe
            Matt Kraai
        Miroslav Lichvar
@@ -59,6 +61,7 @@ For fixes or providing information which led to a fix:
         Antoine Mathys
             Dan McMahill
           Roger Mc Murtrie
+            Tim Mooney
         Han-Wen Nienhuys
             Jan Nieuwenhuizen
          Hrvoje Nikšić