[Rd] back port of Bug 15899 fix missing from R 3.2.1 RC release!!!

[Martin Maechler]

>>>>> Jack Howarth <howarth.mailing.lists at gmail.com>
>>>>>     on Mon, 15 Jun 2015 22:03:59 -0400 writes:

    > Is there a reason why the fix for Bug 15899 - Omitted 'extern' on
    > 'R_running_as_main_program' after refactor can cause linker errors for
    > applications embedding R...

    > https://bugs.r-project.org/bugzilla3/show_bug.cgi?id=15899

    > was never back ported for R 3.3 for the R 3.2.1 release? Restoring
    > that omitted 'extern' to the declaration of 'int
    > R_running_as_main_program;' in src/Rinterface.h is essential for being
    > able to build Rstudio.

from the sources ...(which is unusual, but  I agree that that is
          	 an important exercise .. if only to implicitly "prove" that
     	       	 Rstudio is truly open source...) 

    > Jack

I had not ported that change to R-patched because I had not been
100% sure that there were no "bad" implications -- so wanted to wait a
couple of days -- and then forgot... I am sorry.

Still your "reminder" comes very very late in the release
process for R 3.2.1. ... but as an exception, and because it
*is* so minimal (and has not caused any negative effects)
I have ported the change now to the 3.2.1 RC.

Martin