chore(*): release version 3.4.2

Author: Kha

README.md

@@ -19,7 +19,7 @@ About
 - [Theorem Proving in Lean](https://leanprover.github.io/theorem_proving_in_lean/index.html)
 - [Change Log](doc/changes.md)
 - [FAQ](doc/faq.md)
-- **Important**: Lean 3.4.1 is the latest release. It is also the last release for the Lean 3.x code base. Only major bugs (e.g., soundness) will be fixed for this code base from now on.
+- **Important**: Lean 3.4.2 is the latest release. It is also the last release for the Lean 3.x code base. Only major bugs (e.g., soundness) will be fixed for this code base from now on.
   We are currently developing Lean 4 in a new (private) repository.
   The Lean 4 source code will be released here when ready. The main goals for Lean 4 are described [here](doc/lean4.md).
 - For HoTT mode, please use [Lean2](https://github.com/leanprover/lean2).

src/CMakeLists.txt

@@ -6,7 +6,7 @@ project(LEAN CXX C)
 set(LEAN_VERSION_MAJOR 3)
 set(LEAN_VERSION_MINOR 4)
 set(LEAN_VERSION_PATCH 2)
-set(LEAN_VERSION_IS_RELEASE 0)  # This number is 1 in the release revision, and 0 otherwise.
+set(LEAN_VERSION_IS_RELEASE 1)  # This number is 1 in the release revision, and 0 otherwise.
 set(LEAN_SPECIAL_VERSION_DESC "" CACHE STRING "Additional version description like 'nightly-2018-03-11'")
 set(LEAN_VERSION_STRING "${LEAN_VERSION_MAJOR}.${LEAN_VERSION_MINOR}.${LEAN_VERSION_PATCH}")
 if (LEAN_SPECIAL_VERSION_DESC)