5261 libm should stop using synonyms.h

*** 37,47 ****
   *      if (n<0) n+=1
   *      z = scalbn(x,-n)
   *      LOG2(x) = n + (1/ln2)*log(x)
   */
  
! #pragma weak log2l = __log2l
  
  #include "libm.h"
  #include "longdouble.h"
  
  static const long double
--- 37,47 ----
   *      if (n<0) n+=1
   *      z = scalbn(x,-n)
   *      LOG2(x) = n + (1/ln2)*log(x)
   */
  
! #pragma weak __log2l = log2l
  
  #include "libm.h"
  #include "longdouble.h"
  
  static const long double