fix win32 warning in target.c

This was creating a warning during a win32 build:

```
dmc -c -Iroot;\dm\include -o   -cpp -DDM_TARGET_CPU_X86=1  target
target.c(152) : Warning 18: implied return of Target::critsecsize at closing '}' does not return value
```
Update target.c
Merge pull request #2327 from monarchdodra/warning

fix win32 warning in target.c