When the build system writes an automatically generated file, say what
program generated it and, when applicable, from which source file, to help
us navigate around the build system.  We were doing so in some but not all
cases.

* build/generator/gen_make.py
  (Generator): Refer to this program in transform_libtool_scripts.sh and
    autogen-standalone.mk, and to 'build-outputs.mk' in the latter.

* build/generator/swig/header_wrappers.py
  (Generator): Refer to this program in the header wrapper files. (It
    was already referring to the source header file.)

* tools/dev/gen-py-errors.py
  (HEADER): Correct the name of this program, as written to stdout.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1444799 13f79535-47bb-0310-9956-ffa450edef68