Warn if !packhdr system() call returns non-zero


git-svn-id: https://svn.code.sf.net/p/nsis/code/NSIS/trunk@6536 212acab6-be3b-0410-9dea-997c60f758d6
Added PEDllCharacteristics attribute and changed default DllCharacteristics to TS_AWARE+NO_SEH+NX_COMPAT+DYNAMIC_BASE


git-svn-id: https://svn.code.sf.net/p/nsis/code/NSIS/trunk@6537 212acab6-be3b-0410-9dea-997c60f758d6
* Added IsWow64 to x64.nsh and fixed RunningX64 for 64-bit installers.

* NSIS_AMD64 and NSIS_IX86 defines added for CPU target detection



git-svn-id: https://svn.code.sf.net/p/nsis/code/NSIS/trunk@6538 212acab6-be3b-0410-9dea-997c60f758d6