i386: new stub strategy to avoid problems with early mmap layout

The stub occupies the same region that execve() would create
for the original progam.  The stub copies everything to a new area,
erases the original region, replaces it with the de-compressed
program, and erases the copy of itself via the escape hatch.
The copy is inexpensive via mmap() of /proc/self/exe.

	modified:   stub/src/i386-linux.elf-entry.S
	modified:   stub/src/i386-linux.elf-fold.S
	modified:   stub/src/i386-linux.elf-main.c

	modified:   p_lx_elf.cpp
	modified:   p_lx_elf.h
	modified:   p_lx_interp.cpp
	modified:   p_lx_interp.h
	modified:   p_lx_sh.cpp
	modified:   p_lx_sh.h
	modified:   p_mach.cpp
	modified:   p_mach.h
	modified:   p_unix.cpp
	modified:   p_unix.h
	modified:   p_vmlinx.cpp

	plus .h, .map, .dump

src/p_lx_sh.cpp

@@ -161,11 +161,10 @@ PackLinuxI386sh::pack1(OutputFile *fo, Filter &)
     generateElfHdr(fo, stub_i386_linux_elf_shell_fold, 0x08048000);
 }
 
-void
+off_t
 PackLinuxI386sh::pack3(OutputFile *fo, Filter &ft)
 {
-    super::pack3(fo,ft);
-    elfout.phdr[0].p_filesz = fo->getBytesWritten();
+    return elfout.phdr[0].p_filesz = super::pack3(fo,ft);
 }
 
 /* vim:set ts=4 sw=4 et: */