Push kernel/user limit to 2GiB, so Mach can address up to close to 2GiB memory.
This makes glibc's local-bigmem.diff patch mandatory.

Index: gnumach/i386/include/mach/i386/vm_param.h
===================================================================
--- gnumach.orig/i386/include/mach/i386/vm_param.h	2012-05-05 11:22:08.295629763 +0000
+++ gnumach/i386/include/mach/i386/vm_param.h	2012-05-05 11:25:25.955430280 +0000
@@ -73,6 +73,6 @@
    with that.
    */
 #define VM_MIN_ADDRESS		(0)
-#define VM_MAX_ADDRESS		(0xc0000000UL)
+#define VM_MAX_ADDRESS		(0x80000000UL)
 
 #endif	/* _MACH_I386_VM_PARAM_H_ */
Index: gnumach/i386/Makefrag.am
===================================================================
--- gnumach.orig/i386/Makefrag.am	2012-05-05 11:22:08.291629849 +0000
+++ gnumach/i386/Makefrag.am	2012-05-05 11:26:22.262233815 +0000
@@ -199,7 +199,7 @@ EXTRA_DIST += \
 	i386/ldscript
 if PLATFORM_at
 gnumach_LINKFLAGS += \
-	--defsym _START=0xC0100000 \
+	--defsym _START=0x80100000 \
 	--defsym _START_MAP=0x100000 \
 	-T '$(srcdir)'/i386/ldscript
 endif
Index: gnumach/i386/i386/vm_param.h
===================================================================
--- gnumach.orig/i386/i386/vm_param.h	2012-05-05 11:22:08.295629763 +0000
+++ gnumach/i386/i386/vm_param.h	2012-05-05 11:27:42.380531253 +0000
@@ -37,7 +37,7 @@
 /* This can be changed freely to separate kernel addresses from user addresses
  * for better trace support in kdb; the _START symbol has to be offset by the
  * same amount. */
-#define VM_MIN_KERNEL_ADDRESS	0xC0000000UL
+#define VM_MIN_KERNEL_ADDRESS	0x80000000UL
 /* This must remain 0 */
 #define INIT_VM_MIN_KERNEL_ADDRESS	0x00000000UL
 #endif	/* MACH_XEN */