mmap() with PROT_WRITE on RHEL5 incompatible with RHEL4

Issue

• The problem is page fault code file is different on x86_64 and x86_32 code.
• mmap() with PROT_WRITE only is incompatible between RHEL4 and RHEL5.
• When you mmap() a page with specifying PROT_WRITE only as the 'prot' argument,
  •   (a) if you read the page for the first time, it will cause SIGSEGV,
  •   (b) but if you read it after write it once, this read will succeed.
• This is an inconsistency ((a) SEGV v.s. (b) success) problem, and fixed on RHEL4.5 or later so that the first read (a) will succeed too.