pcmanx-gtk2: add BuildRequires: libtool to fix segmentation fault

This update fixes the following issue for pcmanx-gtk2:
- bnc#779500: add BuildRequires: libtool to fix a segmentation fault in openSUSE 12.2

Fixed bugs
bnc#779500
pcmanx-gtk2 Segmentation fault in openSUSE 12.2
Selected Binaries
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