build: Move wrapped scripts in "bin" directory

build: Move wrapped scripts in "bin" directory

Those scripts are used both in the build process and for the tests, so
it seems clearer to not hide them in "t/wrap" directory.

* t/wrap/aclocal.in: Rename to ...
* bin/wrap-aclocal.in: ... this.
* t/wrap/automake.in: Rename to ...
* bin/wrap-automake.in: ... this.
* configure.ac: Generate "bin/aclocal-${APIVERSION}" and
"bin/automake-${APIVERSION}" at configure time.
* t/Makefile.inc (nodist_noinst_SCRIPTS): Move wrapped scripts ...
* bin/Makefile.inc (nodist_noinst_SCRIPTS): ... here.
* Makefile.am (extend_PATH): Use "bin" directory.
* t/ax/test-defs.in (am_bindir): Likewise.
* t/get-sysconf.sh: Likewise.
* .gitignore: Update.