Clang compiling fixes for narrowed type

## Fixes issues with clang has with compiling ```dcraw_common.cpp```

Fixes:
- Constant expression evaluates to 128 which cannot be narrowed to type
'signed char'  on ```0x80```
- Constant expression evaluates to 136 which cannot be narrowed to type
'signed char' on ```0x88```
- Constant expression evaluates to 65535 which cannot be narrowed to
type 'short' on ```0xffff```
- Invalid suffix on literal; C++11 requires a space between literal and
identifier - on ```strcpy (th->soft, "dcraw v"DCRAW_VERSION);```

Clang version Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM
3.5svn)
Also tested and happening in Apple LLVM 5 and clang 5.