Fix bug #18277 with mouse clicks on R2L lines.

 src/dispnew.c (buffer_posn_from_coords): Fix mirroring of X
 coordinate for hscrolled R2L screen lines.
Avoid inflooping in redisplay caused by hscrolled R2L lines.

 src/xdisp.c (display_line): Don't assume that the call to
 reseat_at_next_visible_line_start ends up at a character
 immediately following the newline on the previous line.  Avoids
 setting the ends_at_zv_p flag on screen lines that are not at or
 beyond ZV, which causes infloop in redisplay.  For the details, see
 http://lists.gnu.org/archive/html/emacs-devel/2014-08/msg00368.html.
* lisp/simple.el (self-insert-uses-region-functions): Defvar.
Fix bug #18276 with vertical motion through a display property.

 src/indent.c (Fvertical_motion): Fix vertical motion up through a
 display property after a newline.
src/xdisp.c (handle_stop): Improve commentary.
* lisp/progmodes/python.el (python-shell-prompt-detect): Remove redundant
executable-find.
* python-tests.el (python-shell-calculate-exec-path-2): Update test
for today's python.el changes.
Update Emacs's bidirectional conformance per Unicode 6.3.0.

 doc/lispref/display.texi (Bidirectional Display): Update the Emacs's class
 of bidirectional conformance.
Backport: * configure.ac (HAVE_XPM): Explain the use of CPPFLAGS in the Cygwin-w32 build.  (Bug#18302)
Fix compilation warnings about snprintf in the MSDOS build.

 msdos/sed2v2.inp [DJGPP <= 2.03]: Add a prototype for snprintf, to
 avoid compilation warning from newer GCC versions that have
 snprintf as a built-in.  Reported by Juan Manuel Guerrero
 <juan.guerrero@gmx.de>.
* emulation/cua-rect.el (cua--highlight-rectangle): Avoid error at point-min.
Fix unoptimized build on MSDOS.

 msdos/sedlibmk.inp (gl_LIBOBJS): Add execinfo.o.  Reported by Juan
 Manuel Guerrero <juan.guerrero@gmx.de>.

 src/conf_post.h (_GL_EXECINFO_INLINE) [MSDOS]: Don't define.
* net/shr.el (shr-expand-url): Plain expand-file-name is not enough;
use url-expand-file-name.
shr.el: Comment.
* net/tramp-adb.el: Spell author name correctly.
* emacs-lisp/authors.el (authors-aliases): Addition.
* sysdep.c (LC_COLLATE, LC_COLLATE_MASK): Give individual defaults.
* etc/emacs.appdata.xml: New file

Ref: http://people.freedesktop.org/~hughsient/appdata/

The description is adapted from the Emacs homepage.
* lisp/subr.el (remq): Revert 2014-08-25 doc change (not always true).

See the interminable bug discussion if you have nothing better to do.
Merge from emacs-24; up to r117462