Import names immediately with COMPOSITE_EXPORT

Import names immediately with COMPOSITE_EXPORT

RFC 6680 specifies that GSS_Export_name_composite() "outputs a token that
"can be imported with GSS_Import_name(), using GSS_C_NT_COMPOSITE_EXPORT
as the name type...".  Therefore, in the gss_import_name mechglue, we
should perform the import process imediately when either
GSS_C_NT_COMPOSITE_EXPORT or GSS_C_NT_EXPORT_NAME are used (not just
for the later, as is the current functionality).

The naming extension test was also updated to display the result
of importing with GSS_C_NT_COMPOSITE_EXPORT in addition to
GSS_C_NT_EXPORT_NAME.

[ghudson@mit.edu: minor style changes]

ticket: 8153 (new)
target_version: 1.13.2
tags: pullup