MFC r293053, r293061, r293063, r293064, r293065, r293775, r293792:

MFC r293053, r293061, r293063, r293064, r293065, r293775, r293792:

  Use 64-bit math when finding a block of ram to hold the kernel.  This fixes
  a problem on 32-bit systems which have ram occupying the end of the physical
  address space -- for example, a block of ram at 0x80000000 with a size of
  0x80000000 was overflowing 32 bit math and ending up with a calculated size
  of zero.

  Use 64-bit math when processing the lists of physical and excluded memory
  to generate the phys_avail and dump_avail arrays.

  Work around problems that happen when there is ram at the end of the
  physical address space.

  Cast pointer through uintptr_t on the way to uint64_t to squelch a warning.

  Reword the comment to better describe what I found while researching the
  problem that led to this temporary workaround (and also so I can properly
  cite the PR in the commit this time).

  Cast using uintfptr_t and eliminate the cast to uint64_t which is uneeded
  because rounding down cannot increase the number of bits needed to express
  the result.

  Go back to using uintptr_t, because code that actually compiles is
  infinitely less buggy than code that is theoretically correct in some
  alternate universe.

PR:           201614

git-svn-id: svn://svn.freebsd.org/base/stable/10@294685 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f