Fix installation with CMake

[PatrickKa]

I wanted to check out and test this reference implementation today but ran into issues when installing it with CMake. More specifically, I found the following two bugs:

• There are typos or copy-paste errors in the target sources for the INSTALL_INTERFACE. The names of the five op_traits_... headers are incorrectly spelled as opt_names... (with an additional t).

  wg21/CMakeLists.txt

  Lines 74 to 78 in b704189

  	$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/linear_algebra/opt_traits_addition.hpp>
  	$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/linear_algebra/opt_traits_division.hpp>
  	$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/linear_algebra/opt_traits_multiplication.hpp>
  	$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/linear_algebra/opt_traits_subtraction.hpp>
  	$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/linear_algebra/opt_traits_support.hpp>

• The matrix header is not installed because it doesn't match the pattern "*.hpp" used in this install() command:

  wg21/CMakeLists.txt

  Lines 106 to 114 in b704189

  	# Hierarchically copy headers to the install dir
  	install (
  	DIRECTORY
  	"${CMAKE_CURRENT_SOURCE_DIR}/include/"
  	DESTINATION
  	${CMAKE_INSTALL_INCLUDEDIR}
  	FILES_MATCHING PATTERN
  	"*.hpp"
  	)