Fix namespace conformance issue with Bessel functions.

[BZ #17747]
The y0/y1/yn and j0/j1/jn functions provided a strong_alias
to the "l"-suffixed variants when no long double support is
being compiled.  This breaks namespace conformance when the
basename versions conform but the l-suffixed ones don't.
Fixed by making them weak aliases instead.

math/w_jn.c

@@ -33,7 +33,7 @@ jn (int n, double x)
   return __ieee754_jn (n, x);
 }
 #ifdef NO_LONG_DOUBLE
-strong_alias (jn, jnl)
+weak_alias (jn, jnl)
 #endif
 
 
@@ -64,5 +64,5 @@ yn (int n, double x)
   return __ieee754_yn (n, x);
 }
 #ifdef NO_LONG_DOUBLE
-strong_alias (yn, ynl)
+weak_alias (yn, ynl)
 #endif