* acinclude.m4 (GDB_AC_DEFINE_RELOCATABLE): New function.
(GDB_AC_WITH_DIR): Call it.
* configure.ac: Define WITH_PYTHON_PATH if we can find the
python installation directory.
* config.in: Regenerate.
* configure: Regenerate.
* defs.h (python_libdir): Declare.
* main.c (python_libdir): Define.
(captured_main): Initialize python_libdir.
* python/python.c (_initialize_python): #ifdef WITH_PYTHON_PATH,
call Py_SetProgramName to make sure python can find its libraries
and modules.