Fix __finitel libm compat symbol version.

The changes to restrict implementation-namespace symbol aliases such
as __finitel to compat symbols used code for __finitel in libm
analogous to that for __finitel in libc.  However, the versions for
the two symbols are actually different, GLIBC_2.0 in libc and
GLIBC_2.1 in libm.  This patch fixes the handling of the libm compat
symbol.

Tested for mips (o32), where it fixes an ABI test failure.

	* sysdeps/ieee754/dbl-64/s_finite.c
	[NO_LONG_DOUBLE && LDBL_CLASSIFY_COMPAT] (__finitel): Define
	compat symbol at version GLIBC_2_1 and use GLIBC_2_1 in
	SHLIB_COMPAT condition for libm, not GLIBC_2_0.
	* sysdeps/ieee754/dbl-64/wordsize-64/s_finite.c
	[NO_LONG_DOUBLE && LDBL_CLASSIFY_COMPAT] (__finitel): Likewise.