Always use c99 float function overloads when using Dinkumware with Visual C++,
as it doesn't always have the C++ overloads. Fixes #2264.
Merged revisions 48529,48674 via svnmerge from
https://svn.boost.org/svn/boost/trunk
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r48529 | danieljames | 2008-09-02 11:31:26 +0100 (Tue, 02 Sep 2008) | 1 line
Always use c99 float function overloads on Dinkumware, as it doesn't always
have the C++ overloads. Refs #2264.
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r48674 | danieljames | 2008-09-08 22:06:16 +0100 (Mon, 08 Sep 2008) | 7 lines
Reinstate the old choice of float functions on Dinkumware for all compilers
other than Visual C++.
It turns out that Borland uses Dinkumware but doesn't have the C99 float
overloads, so it only seems realistic to assume their existence on Visual C++.
Refs #2264.
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