Accidentally didn't implement this for FPREM1 but it /was/ implemented
for FPREM. Fixes an infinite loop in cossin implementations.
Test code from the application returns an incorrect result, but it isn't
due to FPREM1.
```
$ `which wine` ./hello.exe
Sin 1.22460635382238E-16
Cos -1
$ FEXInterpreter `which wine` ./hello.exe
Sin 1.22460635382238E-16
Cos 0.54030230586814
```
Fixes#2021