Was getting these errors:

========
nsterm.h:455: error: expected ‘)’ before ‘instancetype’
nsterm.h:456: error: expected ‘)’ before ‘instancetype’
nsterm.h:460: error: expected ‘)’ before ‘instancetype’
nsterm.h:463: error: expected ‘)’ before ‘instancetype’
nsterm.h:523: error: expected ‘)’ before ‘instancetype’
nsterm.h:557: error: expected ‘)’ before ‘instancetype’
nsterm.h:592: error: expected ‘)’ before ‘instancetype’
nsterm.h:611: error: expected ‘)’ before ‘instancetype’
nsterm.h:659: error: expected ‘)’ before ‘instancetype’
nsterm.h:661: error: expected ‘)’ before ‘instancetype’
nsterm.h:663: error: expected ‘)’ before ‘instancetype’
nsterm.h:664: error: expected ‘)’ before ‘instancetype’
nsterm.h:703: error: expected ‘)’ before ‘instancetype’
nsterm.h:706: error: expected ‘)’ before ‘instancetype’
nsterm.h:710: error: expected ‘)’ before ‘instancetype’
nsterm.h:711: error: expected ‘)’ before ‘instancetype’
nsterm.h:712: error: expected ‘)’ before ‘instancetype’
nsterm.h:735: error: expected ‘)’ before ‘instancetype’
nsterm.m:6900: error: expected ‘)’ before ‘instancetype’
nsterm.m:7630: error: expected ‘)’ before ‘instancetype’
nsterm.m:7655: error: expected ‘)’ before ‘instancetype’
nsterm.m:7681: error: expected ‘)’ before ‘instancetype’
nsterm.m:7909: error: expected ‘)’ before ‘instancetype’
nsterm.m:8261: error: expected ‘)’ before ‘instancetype’
nsterm.m:8345: error: expected ‘)’ before ‘instancetype’
nsterm.m:8353: error: expected ‘)’ before ‘instancetype’
nsterm.m:8408: error: expected ‘)’ before ‘instancetype’
nsterm.m:8487: error: expected ‘)’ before ‘instancetype’
========

   CC       nsmenu.o
nsmenu.m:1496: error: expected ‘)’ before ‘NSWindowStyleMask’
nsmenu.m: In function ‘-[EmacsDialogPanel 
initWithContentRect:styleMask:backing:defer:]’:
nsmenu.m:1498: warning: conflicting types for 
‘-(id)initWithContentRect:(NSRect)contentRect styleMask:(id)aStyle 
backing:(NSBackingStoreType)backingType defer:(BOOL)flag’
/System/Library/Frameworks/AppKit.framework/Headers/NSWindow.h:264: 
warning: previous declaration of 
‘-(id)initWithContentRect:(NSRect)contentRect 
styleMask:(NSUInteger)aStyle backing:(NSBackingStoreType)bufferingType 
defer:(BOOL)flag’
nsmenu.m:1520: warning: assignment makes pointer from integer without a cast
nsmenu.m:1525: warning: passing argument 2 of 
‘initWithContentRect:styleMask:backing:defer:’ makes integer from 
pointer without a cast
========

This is with an LLVM/GCC that came with MacOS 10.6:

i686-apple-darwin10-llvm-gcc-4.2 (GCC) 4.2.1 (Based on Apple Inc. build 
5658) (LLVM build 2335.15.00)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

I've changed the source back to compile correctly (see patch).  It comes 
down to
removing the "instancetype" identifiers and reverting an 
NSWindowStyleMask to an
NSUInteger.

I also see this warning when compiling macfont.m:

macfont.m: In function ‘mac_font_shape_1’:
macfont.m:416: warning: ‘NSLayoutManager’ may not respond to 
‘-getGlyphsInRange:glyphs:properties:characterIndexes:bidiLevels:’
macfont.m:416: warning: (Messages without a matching method signature
macfont.m:416: warning: will be assumed to return ‘id’ and accept
macfont.m:416: warning: ‘...’ as arguments.)

(some new arguments were added in the recent changes).  But this doesn't 
seem to affect functionality so I've left that change as is.