Correct CFLAGS "-Idir" with --sdkroot option

need to add "sdkroot" dir for -I option of ffi and rexml2.
-I/usr/include/ffi -> -I$(SDKROOT)/usr/include/ffi

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2431 f4f36d40-9719-0410-9868-dde021a23eda
Change path of input file at test_s_dataWithContentsOfURL.
Remove unused code to install Project Builder templates