message: Update the INSTALL file.
diff: @@ -442,7 +442,7 @@ Debug and optimization options are controlled through the CMake variable
  CMAKE_BUILD_TYPE which can be set to standard values like "Debug", and "Release"
  (default).
  -To use a non-default generator use the "-G <generator>" option of cmake:
  +To use a specific generator use the "-G <generator>" option of cmake:
  cmake <mfem-source-dir> -G "Xcode"
  cmake <mfem-source-dir> -G "Visual Studio 12 2013"
  @@ -471,11 +471,14 @@ or
  which will simply compile and run Example 1/1p. For more extensive tests that
  check the results from all the serial/parallel MFEM examples and miniapps use:
  + make exec -j 4
  make test
  or
  + cmake --build . --target exec
  cmake --build . --target test
  or
  - cmake --build . --config Release --target test [Visual Studio, Xcode]
  + cmake --build . --config Release --target exec [Visual Studio, Xcode]
  + cmake --build . --config Release --target RUN_TESTS [Visual Studio, Xcode]
  Note that running all the tests may take a while.
  @@ -486,7 +489,8 @@ CMAKE_INSTALL_PREFIX. To install the library, use
  or
  cmake --build . --target install
  or
  - cmake --build . --config Release --target install [Visual Studio, Xcode]
  + cmake --build . --config Release --target install [Xcode]
  + cmake --build . --config Release --target INSTALL [Visual Studio]
  The library will be installed in <PREFIX>/lib, the headers in <PREFIX>/include,
  and the configuration CMake files in <PREFIX>/lib/cmake/mfem.
  