Xcode project generation improvements
2 fixes and 2 feature extensions, relatively independent, but all necessary for me to get Xcode project generation to work for one particular project
- Corrected textual aligment in generated project file (not strictly necessary for machine-read file, but very helpful when manually inspecting result)
- Moved linker flags to the correct place
- Export preprocessor macros
- Escape quoted strings in Xcode project (e.g. string preprocessor symbols)