create_temp_file automatically supplies the test directory and the
XXXXXX suffix. support_create_temp_directory required the caller to
specify them, which was confusing.
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
The new test driver in <support/test-driver.c> has feature parity with
the old one. The main difference is that its hooking mechanism is
based on functions and function pointers instead of macros. This
commit also implements a new environment variable, TEST_COREDUMPS,
which disables the code which disables coredumps (that is, it enables
them if the invocation environment has not disabled them).
<test-skeleton.c> defines wrapper functions so that it is possible to
use existing macros with the new-style hook functionality.
This commit changes only a few test cases to the new test driver, to
make sure that it works as expected.
