Changeset 1412 for trunk/build_support/yat.m4

yat autoconf macro
For details on the macro see header in file.

In the description (refs #283) test was suggested to include tests for
secondary libraries such as GSL. I haven't done that explicitely, but
in the compilation test, I chose to include Vector.h because it uses
both GSL and Boost. The linking requirements are also checked in an
indirect fashion, because if the yat-config file is not manipulated it
should give ldflags to all the required libs such as -lm, which
implies failure if they are not present.

If anyone wants more detailed tests on these packages, I think one
should use macro provided from these projects.

Should describe this and yat-config in README before closing this ticket.