stupid include problems

Probably this is a stupid question, but I don’t understand this problem.
I wanted to include the squirrel scripting language into a cocos2d-x Xcode (Iphone) Project.
But somehow I had some difficulties including all neccessary files. At first squirrel classes did not want to compile.
I had to replace all (#include <xxx.h>) includes with (#include “xxx.h”) and then everything worked.
But I really don’t understand why.
Could someone please explain.
Is there another possibility besides changing all includes in the library?
Greetings
Hannes

If want include c/c++ stdandard library header file , use include , the complier search xxx file begin from std file directory.
If want include other library header file, use include “yyy”, the complier search yyy file begin from user code directory.

Yes, I know, but the files that don’t compile are not mine and I don’t really want to replace all includes. Then I would have to do so every time I upgrade these files to a new version of the library.
Isn’t there some way to tell XCode that if the files included with <xxx.h> where not found in the std file directory to look in the user code directory?
Greetings Hannes