[clang-tidy] Python scripts shebang fixes

Summary:
This patch fixes shebang lines in Python script files.

Most Python scripts in LLVM & Clang are using this shebang line.

[[ https://mail.python.org/pipermail/tutor/2007-June/054816.html | Here]] is an explanaiton of why such line should be used instead of what is currently in these few files.

Reviewers: klimek, alexfh

Subscribers: cfe-commits

Patch by Kirill Bobyrev!

Differential Revision: http://reviews.llvm.org/D16270

llvm-svn: 258133

clang-tools-extra/clang-tidy/tool/clang-tidy-diff.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 #
 #===- clang-tidy-diff.py - ClangTidy Diff Checker ------------*- python -*--===#
 #

clang-tools-extra/docs/clang-tidy/tools/dump_check_docs.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 r"""
 Create stubs for check documentation files.

clang-tools-extra/test/clang-tidy/check_clang_tidy.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 #
 #===- check_clang_tidy.py - ClangTidy Test Helper ------------*- python -*--===#
 #