Unify python executables to use `#!/usr/bin/env python` shebang (#2102)

* fixed shebangs in tools (and lib)

* fixed shebangs in examples

* do not mangle shebangs in rpm spec

* renamed style-check.sh to c-style-check.sh

* factored out python linter to a separate file

* added shebang validation to the py-style-check

* added shebangs to all python executables
diff --git a/tools/sslsniff.py b/tools/sslsniff.py
index 265e87f..f7bc117 100755
--- a/tools/sslsniff.py
+++ b/tools/sslsniff.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 #
 # sslsniff  Captures data on read/recv or write/send functions of OpenSSL,
 #           GnuTLS and NSS