pulseview: new package

[Thomas:
  - Fix dependency on C++, it should use BR2_INSTALL_LIBSTDCPP and not
    BR2_TOOLCHAIN_BUILDROOT_CXX.
  - Fix comment dependency, there should be an || between all the
    toolchain dependencies. Also fix the dependency on Qt5 for the
    comment, which was in the wrong way: the comment was displayed
    only when Qt5 was disabled.
  - Use -DDISABLE_WERROR=TRUE instead of -DDISABLE_WERROR=y, since
    TRUE/FALSE are normally the accepted values for CMake options.]

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>