Merge int_matmult and float_matmult into a single test directory.

These two tests are almost identical except one is on integers and
the other is on floats, and the input data is different.

Merge the tests into a single test directory, share a common source
file, and generate the two binaries there.

ChangeLog:

	* configure.ac: Remove int_matmult and float_matmult, add matmult.
	* configure: Regenerate.
	* src/float_matmult/Makefile.in: Removed.
	* src/float_matmult/matmult.c: Removed.
	* src/float_matmult/Makefile.am: Removed.
	* src/int_matmult/Makefile.am: Removed.
	* src/int_matmult/Makefile.in: Removed.
	* src/int_matmult/matmult.c: Removed.
	* src/matmult/Makefile.am: New file.
	* src/matmult/Makefile.in: New file.
	* src/matmult/matmult.c: New file.