Blender Git Loki

Enable header auto-complete suggestions in Xcode

Description of `USER_HEADER_SEARCH_PATHS` build setting:
"
This is a list of paths to folders to be searched by the compiler
for included or imported user header files (those headers listed
in quotes) when compiling C, Objective-C, C++, or Objective-C++.
Paths are delimited by whitespace, so any paths with spaces in
them need to be properly quoted. See Always Search User Paths
(Deprecated) (ALWAYS_SEARCH_USER_PATHS) for more details
on how this setting is used. If the compiler doesn't support the
concept of user headers, then the search paths are prepended to
the any existing header search paths defined in Header Search
Paths (HEADER_SEARCH_PATHS).
"

http://help.apple.com/xcode/mac/current/#/itcaec37c2a6

Xcode doesn't use `HEADER_SEARCH_PATHS` for auto-complete. Only the
header files in the same directory as the current file are suggested.

CMake as of now correctly sets `SYSTEM_HEADER_SEARCH_PATHS` and lumps the
rest in `HEADER_SEARCH_PATHS`. The standard way is to use
`USER_HEADER_SEARCH_PATHS` & `SYSTEM_HEADER_SEARCH_PATHS` and let
`HEADER_SEARCH_PATHS` be used as a fallback for compilers which do not
distinguish between `<*.h>` and `"*.h"` syntax.

So set `USER_HEADER_SEARCH_PATHS` to the include paths specified
in the `CMakeLists.txt` files of all targets.