x86-64: Use correct ELF values

The x86-64 uses different segment alignment (2MB) and a different
start address.
ELF: Make first PT_LOAD cover headers

This makes it so that the first PT_LOAD segment covers
ELF and program header and .interp (contained in the same page anyway,
right before the start of the first loaded section).  binutils
strip creates invalid output otherwise (which strictly is a binutils
bug, but let's be nice anyway).

Conflicts:

	tccelf.c