Clean up ARM old-ABI symbol versioning relics.

Clean up ARM old-ABI symbol versioning relics.

This patch cleans up some symbol versioning code in the ARM port that
exists only as relics of the old-ABI port, which was removed some time
ago.

The minimum symbol version in the ARM port is GLIBC_2.4 (the version
where the EABI port was introduced).  Thus, any SHLIB_COMPAT
conditionals where the later version is 2.4 or later are obsolete and
can be removed.  In addition, there is no need to set symbol versions
before 2.4 explicitly if the symbols would have a version of 2.4 by
default anyway.  This includes most of the entries in
sysdeps/unix/sysv/linux/arm/Versions: those for GLIBC_2.0 are for
libgcc unwind functions that aren't actually in ARM EABI glibc at all,
while those for GLIBC_2.2 and GLIBC_2.3.3 are for functions which for
the old-ABI port may have had versions different from the
architecture-independent default, but where for EABI the default
suffices (both the default and the version in that file map to 2.4, so
the entries in that file do nothing).  The GLIBC_2.1 entries are
needed (architecture-specific functions), but it seems less confusing
for those to say GLIBC_2.4, as the actual version those symbols in
fact have.

Various cases in the <fenv.h> functions where a function is defined as
__fe* with an fe* versioned alias are cleaned up just to define fe*
directly, as done e.g. on AArch64.  If in future we actually need an
__fe* name for use from C90 functions in libm as discussed recently,
of course we can add one on all architectures and make the fe* name
into a weak alias for that particular function, but for now the __fe*
names aren't needed.

In the case of posix_fadvise64, the __posix_fadvise64_l64 name and
posix_fadvise64 alias are kept as __posix_fadvise64_l64 is used in
posix_fadvise.  (For that to be a namespace-clean use, posix_fadvise64
needs to be a *weak* alias not a strong one as at present, but that's
an independent preexisting bug.)

(There remain references to GLIBC_2_2 in
sysdeps/unix/sysv/linux/arm/{msgctl.c,semctl.c,shmctl.c}.  As those
files are used by alpha which has a genuine 2.2 version for those
functions, I think those references need to stay as-is.)

Tested that the disassembly of installed shared libraries is unchanged
by this patch (though function names shown in disassembly change to no
longer have @@GLIBC_2.4, now those functions get versioned only by the
version map and not redundantly at assembler time) and that the ABI
tests pass.

	* sysdeps/arm/fclrexcpt.c (__feclearexcept): Rename to
	feclearexcept.  Remove symbol versioning code.
	* sysdeps/arm/fegetenv.c (__fegetenv): Rename to fegetenv.  Remove
	symbol versioning code.
	* sysdeps/arm/fesetenv.c (__fesetenv): Rename to fesetenv.  Remove
	symbol versioning code.
	* sysdeps/arm/feupdateenv.c (__feupdateenv): Rename to
	feupdateenv.  Remove symbol versioning code.
	* sysdeps/arm/fgetexcptflg.c (__fegetexceptflag): Rename to
	fegetexceptflag.  Remove symbol versioning code.
	* sysdeps/arm/fsetexcptflg.c (__fesetexceptflag): Rename to
	fesetexceptflag.  Remove symbol versioning code.
	* sysdeps/unix/sysv/linux/arm/Versions (libc): Remove GLIBC_2.0,
	GLIBC_2.2 and GLIBC_2.3.3 entries.  Change GLIBC_2.1 to GLIBC_2.4.
	* sysdeps/unix/sysv/linux/arm/posix_fadvise64.c
	(__posix_fadvise64_l32): Remove prototype.
	[SHLIB_COMPAT(libc, GLIBC_2_2, GLIBC_2_3_3)]: Remove conditional
	code.