Remove COLLISION_CHECK from Makefile since it's not used.

It's rather misleading to have configuration options that don't do
anything.  If someone adds collision checking they might also want to
restore this option.

Signed-off-by: Brian Gernhardt <benji@silverinsanity.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Makefile

@@ -82,10 +82,6 @@ all:
 # Define NO_ACCURATE_DIFF if your diff program at least sometimes misses
 # a missing newline at the end of the file.
 #
-# Define COLLISION_CHECK below if you believe that SHA1's
-# 1461501637330902918203684832716283019655932542976 hashes do not give you
-# sufficient guarantee that no collisions between objects will ever happen.
-#
 # Define USE_NSEC below if you want git to care about sub-second file mtimes
 # and ctimes. Note that you need recent glibc (at least 2.2.4) for this, and
 # it will BREAK YOUR LOCAL DIFFS! show-diff and anything using it will likely

configure.ac

@@ -316,10 +316,6 @@ GIT_PARSE_WITH(iconv))
 
 ## --enable-FEATURE[=ARG] and --disable-FEATURE
 #
-# Define COLLISION_CHECK below if you believe that SHA1's
-# 1461501637330902918203684832716283019655932542976 hashes do not give you
-# sufficient guarantee that no collisions between objects will ever happen.
-#
 # Define USE_NSEC below if you want git to care about sub-second file mtimes
 # and ctimes. Note that you need recent glibc (at least 2.2.4) for this, and
 # it will BREAK YOUR LOCAL DIFFS! show-diff and anything using it will likely