Remove BeOS DR8 specific hack

It is already partially removed from screen.c
Remove BEOS_PR_OR_BETTER
Show +cursorshape in :version

All code which was inside #ifdef CURSOR_SHAPE is being used now, except
one in version.c (that occurence is fixed by this commit).
Remove DONT_ADD_PATHSEP_TO_DIR used only in legacy Mac
Remove EBCDIC: Clean up comments
Remove EBCDIC: remove last #ifdef EBCDIC
Remove EBCDIC: Remove IF_EB macros
Remove FEAT_OSFILETYPE

Feature description from Vim documentation:

NOTE: this code is currently disabled, as the RISC OS implementation was
removed.  In the future this will use the 'filetype' option.

On operating systems which support storing a file type with the file, you can
specify that an autocommand should only be executed if the file is of a
certain type.

The actual type checking depends on which platform you are running Vim
on; see your system's documentation for details.

To use osfiletype checking in an autocommand you should put a list of types to
match in angle brackets in place of a pattern, like this: >

	:au BufRead *.html,<&faf;HTML>  runtime! syntax/html.vim

This will match:

- Any file whose name ends in ".html"
- Any file whose type is "&faf" or "HTML", where the meaning of these types
  depends on which version of Vim you are using.
  Unknown types are considered NOT to match.
Remove FEAT_TAG_ANYWHITE

This feature allow to use any white space characters instead of one
<TAB> in tag files. It is disabled in vanilla Vim's default build
configuration. Exuberant ctags use format with exactly one TAB.
Remove HAVE_TOTAL_MEM

libuv provide uv_get_total_mem_kib. So HAVE_TOTAL_MEM should always be
true.
Before that commit in neovim maxmem=5120 and maxmemtot=10240. Now
both equal to half of system memory.
Remove HAVE_LIBC_H

It was used in Vim for NeXT OS.
Remove __MVS__ and MOTIF390_MNEMONIC_FIXED
Remove SMALL_MALLOC. Used on MSDOS and WIN16.
Remove fix for select(). select() is not used anymore.
Merge #814 'Remove dead #ifdefed code'