Removal of unexec support from glibc malloc

[Wolfgang Jenkner]

On Mon, Jan 18 2016, Paul Eggert wrote:

> ./configure emacs_cv_var_doug_lea_malloc=no
>
> This causes Emacs to use its own malloc implementation. Back then
> I observed that this hurt performance somewhat (text 0.5% larger, data
> 7.6% larger, 14% more CPU time on my usual benchmark) but I did not
> observe any bugs; see
> <https://lists.gnu.org/archive/html/emacs-devel/2014-02/msg00542.html>.

IIUC, this means that either mmap or src/ralloc.c is needed for memory
reallocations, and those do have very annoying performance problems in
non-contrived cases, please see bug#19393 for such a scenario.

The discussion about the performance problem begins at

http://debbugs.gnu.org/cgi/bugreport.cgi?bug=19393#46