Document the existence of the otp_build update_primary command,
to verify that the bootstrap beam files match the source files.

Ensure that we cannot get any dangling pointers into code that
has been purged. This is done by a two phase purge. At first
phase all fun entries pointing into the code to purge are marked
for purge. All processes trying to call these funs will be suspended
and by this we avoid getting new direct references into the code.
When all processes has been checked, these processes are resumed.

The new purge strategy now also completely ignore the existence of
indirect references to the code (funs). If such exist, they will
cause bad fun exceptions to the caller, but will not prevent a
soft purge or cause a kill of a process having such live references
during a hard purge. This since it is impossible to give any
guarantees that no processes in the system have such indirect
references. Even when the system is completely clean from such
references, new ones can appear via distribution and/or disk.

* RicoAntonioFelix/patch-1/PR-1003:
  Update INSTALL.md

* Fixed a grammatical error.

Remove the options:

  --enable-darwin-universal
  --enable-darwin-64bit

The --enable-darwin-universal option turns on universal binaries
(Intel/PPC). It does not work on modern releases of OS X, and
OTP 19 will most not likely build on an OS X release that still
supports universal builds.

The --enable-darwin-64bit option is not needed, because 64-bit builds
are default on modern OS X releases. There is also the generic
--enable-m64-build option.

* henrik/doc-fixes:
  Fix typo in INSTALL.md
  Update README.md
  Fix typo in 'app' documentation
  s/is/are

* maint:
  Update preloaded module
  typos

Conflicts:
	erts/preloaded/ebin/prim_file.beam