Add log2 support and make log10 obsolete for consistency.

* configure.ac (log2): Check for this function.
* doc/lispref/numbers.texi (Math Functions): Remove obsolete function log10.
* lisp/subr.el (log10): Move here from C code, and declare as obsolete.
All uses of (log10 X) replaced with (log X 10).
* src/floatfns.c (Flog) [HAVE_LOG2]: Use log2 if available and if the
base is 2; this is more accurate.
(Flog10): Move to Lisp (marked obsolete there).

1 files changed, 4 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index f73ab05e910..097a099b56f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2013-06-20  Rüdiger Sonderfeld <ruediger@c-plusplus.de>
+
+        * configure.ac (log2): Check for this function.
+
 2013-06-19  Juanma Barranquero  <lekktu@gmail.com>
 
         * .bzrignore: Add GNU GLOBAL files.