Do not use implicit int -> bool conversion (not valid in D)
Explicitly cast Type* to char*
Do not set boolean with +=
Use const char[] for constant message string
Clean up interpretCommon function pointers
Reuse the function pointer definition from expression.h for apply
Merge pull request #2406 from yebblies/setboolean

[DDMD] Do not set boolean with +=
Merge pull request #2405 from yebblies/typechar

[DDMD] Explicitly cast Type* to char*
Merge pull request #2404 from yebblies/isunionbool

[DDMD] Do not use implicit int -> bool conversion (not valid in D)
Merge pull request #2407 from yebblies/constmessage

[DDMD] Use const char[] for constant message string
Merge pull request #2416 from yebblies/applyfp2

[DDMD] Reuse the function pointer definition from expression.h for apply
Merge pull request #2415 from yebblies/icfp

[DDMD] Clean up interpretCommon function pointers