pgsql: New method for preventing compile-time calculation of degree con

New method for preventing compile-time calculation of degree constants.

Commit 65abaab547a5758b tried to prevent the scaling constants used in
the degree-based trig functions from being precomputed at compile time,
because some compilers do that with functions that don't yield results
identical-to-the-last-bit to what you get at runtime. A report from
Peter Eisentraut suggests that some recent compilers are smart enough
to see through that trick, though. Instead, let's put the inputs to
these calculations into non-const global variables, which should be a
more reliable way of convincing the compiler that it can't assume that
they are compile-time constants. (If we really get desperate, we could
mark these variables "volatile", but I do not believe we should have to.)

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/6b1a213bbd6599228b2b67f7552ff7cc378797bf

Modified Files
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src/backend/utils/adt/float.c | 49 ++++++++++++++++++++++++-------------------
1 file changed, 27 insertions(+), 22 deletions(-)