this could cause synchronization issues when data is decompressed in a page's leave function and the user clicks the next button twice really fast or on a slow computer.
WM_COMMAND would be sent twice and so DialogProc could execute the leave function while the installation thread is running causing interpreter havoc.
for more details:
http://forums.winamp.com/showthread.php?s=&threadid=274333
as always, a few size optimizations were thrown in the loop and the fix actually makes the code smaller
git-svn-id: https://svn.code.sf.net/p/nsis/code/NSIS/trunk@5313 212acab6-be3b-0410-9dea-997c60f758d6
32854c2021
