Check*.cmake : Add CMAKE_REQUIRED_QUIET flag.

Setting this flag can silence messages from the Check*.cmake modules.
This can be used by Find*.cmake modules when they are in silent mode.
Find*: Make find_package(.. QUIET) affect Check* modules.

Fixes issues #14812 and #14813 where find_package(OpenMP QUIET) and
find_package(Qt4 QUIET) would still print out messages when calling
check*() functions.

Also a partial fix for  #14445 where building CMake
(without cmake-gui) when Qt5 is installed and Qt4 is not installed
and warnings come out of FindQt4.cmake.
cmake-gui: Don't resolve symlinks with using file dialog.

This fixes bug #14274 where a clang++ symlink was resolved to
a clang executable.
Merge topic 'cmake-gui-symlinks' into next

480be00b cmake-gui: Don't resolve symlinks with using file dialog.
Merge topic 'find_package-check-quiet' into next

83934757 Find*: Make find_package(.. QUIET) affect Check* modules.
4c0cc9ab Check*.cmake : Add CMAKE_REQUIRED_QUIET flag.