new macros AX_PATH_BDB and AX_COMPARE_VERSION

[Guido Draheim]

Hi ac-archive people,

I did just check in two new macros by Tim Toolan [toolan-at-ele.uri.edu]"
  legacy/installed_packages/ax_path_bdb.m4
  legacy/misc/ax_compare_version.m4

The ax_path_bdb uses the ax_compare_version macro quite heavily.
It is used to check for a good pair of Berkeley BDB headers and library
settings under the expected name of BDB_(LIBS,*FLAGS). This is quite
a tricky task since many installations have multiple instances of that
library around, sometimes different versions or even different developers.

The macro is very sophisticated, and Tim and I have already gone trough
some iterations of code review - it should now even be able to work in
cross compile mode. The macro surely beats many other submissions
on the scale of usefulness as well as its great m4/sh coding style.

Great work, Tim!
Have fun,
-- guido                                  http://google.de/search?q=guidod
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