* src/Makefile.am (stamp-rtlib-files): New.  This does what was
formerly done by configure.
(common_nsi): Add that new dependency
(stamp-addditional-signedfiles): Skip non-existent files and add
AUTHENTICODE_FILES_OPTIONAL.
* src/gpg4win.mk.in (AUTHENTICODE_FILES): Factor some files out to ...
(AUTHENTICODE_FILES_OPTIONAL): new.  Adjust names.
($(stampdir)/stamp-$(1)-00-install): Avoid mkdir error for an existent
directory.
($(stampdir)/stamp-$(1)-01-install-dev): Ditto.
* src/nsis/gpg4win.nsi: Add build directory includes.  Change
directory defines.
* src/nsis/inst-compendium.nsi: Take the comendium from the source
dir.
* src/nsis/inst-gnupg-w32.nsi: Take the .bat files from the source
dir.
* src/nsis/inst-kleopatra.nsi: Ditto for a couple of other distributed
files.
* src/nsis/inst-qtbase.nsi: Ditto for qt.conf.
* src/nsis/gpg4win-src.nsi: Change diretcory defines.  Not tested but
this file is not anymore used.