MFC r289477:
Fix a strange macro re-definition compile error. If the VM_MAXUSER_ADDRESS value is defined as a config option the definition is emitted into opt_global.h which is force-included into everything. In addition, the symbol is emitted by the genassym mechanism, but that by its nature reduces the value to a 0xnnnnnnnn number. When compiling a .S file you end up with two different definitions of the macro (they evaluate to the same number, but the text is different, upsetting the compiler).