Remove incorrect trailing backslash

If this backslash is here and USE_VALGRIND is defined, valgrind complains that "else" is not a command.
revert #652

reverting broad cosmetic/style change because:
- increases merge-conflicts
- increases overhead of merging upstream Vim patches
- reasons for change are ambiguous, so default to no change
Replace 'alloc' with 'xmalloc' in some files.

Files changed: charset.c, buffer.c, diff.c, edit.c,
ex_cmds.c, ex_cmds2.c and ex_docmd.c.

The remaining alloc's in these files require more careful attention to
remove.
Added missing #define guards in headers
Extract strings.c from misc2.c
Move `concat_strings` from path.c
Remove two-iteration loop from ExpandGeneric
Remove two-iteration loop from expand_filename
Remove two-iteration loop from check_keyword_id
Remove checks for SHORT_FNAME and USE_LONG_FNAME.

They were only defined for MSDOS which is now unsupported.
Don't retry to make the tempname in write_viminfo() with shortname=1

ref #572
Remove the code related to the shortname option
Remove the always-FALSE shortname argument from buf_modname()
Rename buf_modname to modname as they've become the same
Update README: progress section
Improve test_eval.in

The old version required to change the range given to :w for each new
test. Now a new buffer is used instead.