Remove some redundant computations in s_sin.c

There are multiple points in the code where the absolute value of a
number is computed multiple times or is computed even though the value
can only be positive.  This change removes those redundant
computations.  Tested on x86_64 to verify that there were no
regressions in the testsuite.
Remove redundant arguments in reduce_and_compute

The A and DA arguments in reduce_and_compute are useless and hence
have been removed.
Remove more redundant computations in s_sin.c

Removed more redundant computations in the slow paths of the sin and
cos functions.  The notable change is the passing of the most
significant bits of X to the slow functions to check if X is positive
so that just the absolute value of x can be passed and the repeated
ABS() operation is avoided.
Consolidate code to compute sin and cos from lookup tables

This patch consolidates the multiple copies of code that looks up sin
and cos of a number from the lookup table and computes the final
value, into static functions.  This does not have a noticeable
performance impact since the functions are inlined by gcc.

There is further scope for consolidation in the functions but they
cause a more noticable impact on performance (>5%) due to which I have
held back on them.