Simplify close(2) EINTR handling.

This doesn't affect code like Chrome that correctly ignores EINTR on
close, makes code that tries TEMP_FAILURE_RETRY work (where before it might
have closed a different fd and appeared to succeed, or had a bogus EBADF),
and makes "goto fail" code work (instead of mistakenly assuming that EINTR
means that the close failed).

Who loses? Anyone actively trying to detect that they caught a signal while
in close(2). I don't think those people exist, and I think they have better
alternatives available.

Bug: https://code.google.com/p/chromium/issues/detail?id=269623
Bug: http://b/20501816
Change-Id: I11e2f66532fe5d1b0082b2433212e24bdda8219b

libc/arch-arm64/syscalls/___close.S

@@ -2,7 +2,7 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY(close)
+ENTRY(___close)
     mov     x8, __NR_close
     svc     #0
 
@@ -11,4 +11,5 @@ ENTRY(close)
     b.hi    __set_errno_internal
 
     ret
-END(close)
+END(___close)
+.hidden ___close