Remove configure dependency on nonstandard echo -n

Hello!

LibRaw wasn't building properly on Mac OS X 10.10.1. This fix allows a proper "configure" file to be generated.

Errors fixed with this fix:
```
LibRaw p$ autoreconf
configure.ac:2: warning: AC_INIT: not a literal: -n 0.17.0-PreAlpha
configure.ac:2: warning: AC_INIT: not a literal: -n 0.17.0-PreAlpha
configure.ac:2: warning: AC_INIT: not a literal: -n 0.17.0-PreAlpha
configure.ac:2: warning: AC_INIT: not a literal: -n 0.17.0-PreAlpha
configure.ac:9: error: required file './compile' not found
configure.ac:9:   'automake --add-missing' can install 'compile'
...
LibRaw p$ ./configure
./configure: line 4: .: filename argument required
.: usage: . filename [arguments]
LibRaw p$ 
```

/bin/sh has the following behavior:
```sh
sh-3.2$ echo -n Please dont print a newline
-n Please dont print a newline
sh-3.2$
```

printf is a more standard command for controlling the printing of the newline.