glfw: Update GLFW to current master

glfw/glfw@5595fa3ae6 implements a proper fix for the macOS Mojave
problem of OpenGL windows not being rendered until moved or manually
updated.

Pull in the current master and rebase the three patches we have on top:
- two commits we have for reuse of the GLFW CMake build system for Wayland
It hasn't yet to be acknowledged upstream.
- one commit removing #include <windows.h> in glfw3native.h to avoid
duplicate declarations.

Fixes #655 and #665.

src/external/glfw/CMake/modules/FindMir.cmake

@@ -1,34 +0,0 @@
-# FindMir
-# -------
-# Finds the Mir library
-#
-# This will will define the following variables::
-#
-# MIR_FOUND        - the system has Mir
-# MIR_INCLUDE_DIRS - the Mir include directory
-# MIR_LIBRARIES    - the Mir libraries
-# MIR_DEFINITIONS  - the Mir definitions
-
-
-find_package (PkgConfig)
-if(PKG_CONFIG_FOUND)
-  pkg_check_modules (PC_MIR mirclient>=0.26.2 QUIET)
-
-  find_path(MIR_INCLUDE_DIR NAMES mir_toolkit/mir_client_library.h
-                            PATHS ${PC_MIR_INCLUDE_DIRS})
-
-  find_library(MIR_LIBRARY NAMES mirclient
-                           PATHS ${PC_MIR_LIBRARIES} ${PC_MIR_LIBRARY_DIRS})
-
-  include (FindPackageHandleStandardArgs)
-  find_package_handle_standard_args (MIR
-                                     REQUIRED_VARS MIR_LIBRARY MIR_INCLUDE_DIR)
-
-  if (MIR_FOUND)
-    set(MIR_LIBRARIES ${MIR_LIBRARY})
-    set(MIR_INCLUDE_DIRS ${PC_MIR_INCLUDE_DIRS})
-    set(MIR_DEFINITIONS -DHAVE_MIR=1)
-  endif()
-
-  mark_as_advanced (MIR_LIBRARY MIR_INCLUDE_DIR)
-endif()