Remove USE_CR and tag_fgets. #808

These features are only used by legacy Mac OS.
vim-patch:7.4.292  #754

Problem:    Searching for "a" does not match accented "a" with new regexp
            engine, does match with old engine. (David Bürgin)
            "ca" does not match "ca" with accented "a" with either engine.
Solution:   Change the old engine, check for following composing character
            also for single-byte patterns.

https://code.google.com/p/vim/source/detail?r=60cdaa05a6ad31cef55eb6b3dc1f57ecac6fcf79
vim-patch:7.4.290  #753

Problem:    A non-greedy match followed by a branch is too greedy. (Ingo
            Karkat)
Solution:   Add NFA_MATCH when it is already in the state list if the position
            differs.

https://code.google.com/p/vim/source/detail?r=b871734bf54ea185dbd2cc759d86dbfbe21cde26
FileID: implement `FileID` struct

`FileID` should encapsulate `st_dev` and `st_ino`. It is a new abstraction
used to check if two files are the same. `FileID`s will be embeded inside
other struts like `buf_t` or `ff_visited_T`, where a full `FileInfo` would be
to big.
FileID: remove `INVALID_DEVICE_ID` macro
FileID: refactor buffer.c to use `FileID`
FileID: refactor ex_cmds2.c to use `FileID`
FileID: refactor file_search.c to use `FileID`
FileID: refactor if_cscope.c to use `FileID`
FileID: refactor path.c to use `FileID`
FileID: refactor os_unix.c to use `FileID`
FileID: make `os_stat()` static
FileID: remove last use of `st_ino` in memline.c

* FileID can’t be used in memline.c, because the block0 is defined to
use only a 32bit ino.
* implemented `os_file_info_get_inode`
* deprecated `os_file_info_get_inode
FileID: remove `CHECK_INODE` macro