Strange upgrade order.

[Erwan David]

I forgot : upgrading only netpbm gives the same error

/usr/bin/ld: Undefined symbols:
_pnm_xeltopixel
collect2: ld returned 1 exit status
gnumake[2]: *** [pnmtopng] Error 1
gnumake[1]: *** [other/all] Error 2
gnumake: *** [converter/all] Error 2

so there is certainly a problem with the netpbm port, but it does not explain why port
tried foirts to upgrade the dependent package then tried to deactivate a second time libpng.

-- 
Erwan