Revert "bindings/Makefile.am: Fix a bug that happened when src and build directory...

Revert "bindings/Makefile.am: Fix a bug that happened when src and build directory are not the same."

This reverts commit 61f5c1a972626212aab60c4d50f45097485b8e51 which had the
following problems:

 * parts of the build process took place in the source directory (which should
   be read-only though)

 * the "perl" target should not be renamed - the name is used in
   @PERL_BINDINGS@ to identify the bindings that are supposed to be built

Signed-off-by: Sebastian Harl <sh@tokkee.org>
Signed-off-by: Florian Forster <octo@huhu.verplant.org>