Regression test README

The src/test/regress/README file is gone, but still referred to by the
INSTALL file.  We need some place to point the user for information when
they run the regression test.

Unless someone has a better idea, I would put the 'make check' after 'make
install' in the order of instructions, so that they have the HTML docs
installed when they run the tests, so we just point them there.

-- 
Peter Eisentraut   peter_e@gmx.net   http://funkturm.homeip.net/~peter