sincos: Simplify declaration headers.

This follows the same pattern as modf and fract.
Reviewer: Aaron Watry
Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

llvm-svn: 356028
GitOrigin-RevId: 4a725996e5f6688b3177021fb47f0b0570985ce1
1 file changed