wflinfo: add GLSL version information to wflinfo

For versions that do not provide a shader version (GL ES 1.x, GL < 2.0)
print "None", otherwise print the value of GL_SHADING_LANGUAGE_VERSION.

None was picked because it is simple, obvious, and unlike N/A can't be
expanded into multiple meanings

v2: - Don't print for gles1, since gles1 doesn't have a shading language
      and will always return FLINFO_GL_ERROR
v3: - Print 'None' for GL ES 1.x and GL < 2.0
    - Only print shader_version in verbose mode

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>