only use /FIXED for stubs and especially not for DLLs

git-svn-id: http://svn.code.sf.net/p/nsis/code/NSIS@6570 212acab6-be3b-0410-9dea-997c60f758d6
Warn if MUI_LANGUAGE is inserted before MUI_[UN]PAGE_*


git-svn-id: http://svn.code.sf.net/p/nsis/code/NSIS@6572 212acab6-be3b-0410-9dea-997c60f758d6