update for final rounds, clang-format related values

The use of `cindent(1)` and `indent(1)` by the IOCCC Judges
during final round processing has been deprecated in favor
of the `clang-format(1)` tool.

Removed rules in `1337.mk` related to `cindent(1)` and `indent(1)`.

Added `make clang-format` rule to `1337.mk`.

Added `${CLANG_FORMAT}` Makefile variable to `var.mk`.

Created `.clang-format` to hold the IOCCC style, a style that
is somewhat similar to the Linux Kernel style.

var.mk

@@ -39,6 +39,7 @@ CHGRP= chgrp
 CHMOD= chmod
 CKSUM= cksum
 CLANG= clang
+CLANG_FORMAT= clang-format
 CLANG_PLUSPLUS= clang++
 CLEAR= clear
 CMP= cmp