Reduce Math object binary size. (#1491)

Although many Math built-in functions have a similar structure
these code paths were implemented as separate C functions.
After this patch only one common dispatcher remains which shares
the common code paths of different built-in functions. This
reduces the binary size by 1 Kbyte.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg [email protected]

Author: zherczeg