Bug report #330  -  Preview Window case a Synfig Studio crash

I have disabled Preview Window (sensitive = false) thrue the "dialog-flipbook" action (yes it's the call the preview window :) until the Preview Option is called (and the preview window created.)
Then, the action is always enabled (the preview window is only hided on close_event, never closed)

Possible improvement, let Preview Window action always sensitive and call Preview Option the first time.
Merge pull request #61 from d-j-a-y/master

Bug report #330  -  Preview Window case a Synfig Studio crash
Fix complain about uint32_t and uint16_t already defined in /usr/include/stdint.h. Happens on Debian Etch.

Error text:

filecontainerzip.cpp: In member function 'virtual bool synfig::FileContainerZip::open(const std::string&)':
filecontainerzip.cpp:315: error: reference to 'uint16_t' is ambiguous
/usr/include/stdint.h:50: error: candidates are: typedef short unsigned int uint16_t
...
filecontainerzip.cpp:427: error: reference to 'uint32_t' is ambiguous
/usr/include/stdint.h:52: error: candidates are: typedef unsigned int uint32_t
filecontainerzip.cpp:55: error:                 typedef unsigned int synfig::FileContainerZip_InternalStructs::uint32_t
Add compatibility code for older Gtk versions
Make sure we have zlib configured