Allow use of run-time OS version checks on macOS (bug#27810)

Allow use of run-time OS version checks on macOS (bug#27810)

* src/nsterm.h (NSWindowTabbingMode): Define in pre-Sierra macOS.
(MAC_OS_X_VERSION_10_6, MAC_OS_X_VERSION_10_7, MAC_OS_X_VERSION_10_8,
MAC_OS_X_VERSION_10_9, MAC_OS_X_VERSION_10_12, HAVE_NATIVE_FS): Remove
defines.
(NSWindowStyleMaskFullScreen,
NSWindowCollectionBehaviorFullScreenPrimary,
NSApplicationPresentationFullScreen,
NSApplicationPresentationAutoHideToolbar): Define in macOS 10.6.
* src/nsterm.m (colorForEmacsRed, colorUsingDefaultColorSpace,
check_native_fs, ns_read_socket, ns_select, runAlertPanel,
initFrameFromEmacs, windowDidMiniaturize, windowDidEnterFullScreen,
windowDidExitFullScreen, isFullscreen, updateCollectionBehavior,
toggleFullScreen, constrainFrameRect, scrollerWidth, syms_of_nsterm):
Allow use of run-time checks and replace version check macros.
* src/nsfns.m (ns_screen_name): Use run-time OS version checks.
* src/macfont.m (macfont_draw): Use run-time OS version checks.
* src/nsmenu.m (menuWillOpen): Use run-time OS version checks.

Co-authored-by: Charles A. Roelli <charles@aurox.ch>