Fix nsmenu compilation under macOS 10.6

Fix nsmenu compilation under macOS 10.6

* src/nsmenu.m ([EmacsMenu fillWithWidgetValue:]): Replace modern
shorthand dictionary and array definitions.
* src/nsterm.h (NSTextAlignmentRight): Redefine if necessary.
* src/macfont.m (mac_font_create_preferred_family_for_attributes):
isOperatingSystemAtLeastVersion is new in macOS 10.10, so it's
probably wrong to use it to check whether we're below 10.9.
(mac_font_copy_default_descriptors_for_language):
(mac_font_copy_default_name_for_charset_and_languages): It seems these
functions are only used on macOS 10.8 and below.
* src/nsterm.m ([NSColor colorUsingDefaultColorSpace]): Use the
generic colorspace.
(ns_parent_window_rect):
(ns_frame_scale_factor):
([EmacsWindow setParentChildRelationships]): Fix macOS version stuff.

Co-authored-by: Po Lu <luangruo@yahoo.com>