5261 libm should stop using synonyms.h

*** 24,35 ****
  /*
   * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
- #pragma weak exp10 = __exp10
- 
  /* INDENT OFF */
  /*
   * exp10(x)
   * Code by K.C. Ng for SUN 4.0 libm.
   * Method :
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