refactor(printf): move "printf_config.h" include to header

Necessary because PRINTF_OVERRIDE_LIBC is needed in header 
Closes #4

printf.c

@@ -35,43 +35,38 @@
 
 #include "printf.h"
 
-// define this globally (e.g. gcc -DPRINTF_INCLUDE_CONFIG_H ...) to include the
-// printf_config.h header file
-#ifdef PRINTF_INCLUDE_CONFIG_H
-  #include "printf_config.h"
-#endif
 
 // 'ntoa' conversion buffer size, this must be big enough to hold one converted
 // numeric number including padded zeros (dynamically created on stack)
 // default: 32 byte
 #ifndef PRINTF_NTOA_BUFFER_SIZE
-  #define PRINTF_NTOA_BUFFER_SIZE    32U
+#define PRINTF_NTOA_BUFFER_SIZE    32U
 #endif
 
 // 'ftoa' conversion buffer size, this must be big enough to hold one converted
 // float number including padded zeros (dynamically created on stack)
 // default: 32 byte
 #ifndef PRINTF_FTOA_BUFFER_SIZE
-  #define PRINTF_FTOA_BUFFER_SIZE    32U
+#define PRINTF_FTOA_BUFFER_SIZE    32U
 #endif
 
 // support for the floating point type (%f)
 // default: activated
 #ifndef PRINTF_DISABLE_SUPPORT_FLOAT
-  #define PRINTF_SUPPORT_FLOAT
+#define PRINTF_SUPPORT_FLOAT
 #endif
 
 // support for the long long types (%llu or %p)
 // default: activated
 #ifndef PRINTF_DISABLE_SUPPORT_LONG_LONG
-  #define PRINTF_SUPPORT_LONG_LONG
+#define PRINTF_SUPPORT_LONG_LONG
 #endif
 
 // support for the ptrdiff_t type (%t)
 // ptrdiff_t is normally defined in <stddef.h> as long or long long type
 // default: activated
 #ifndef PRINTF_DISABLE_SUPPORT_PTRDIFF_T
-  #define PRINTF_SUPPORT_PTRDIFF_T
+#define PRINTF_SUPPORT_PTRDIFF_T
 #endif
 
 ///////////////////////////////////////////////////////////////////////////////

printf.h

@@ -35,6 +35,13 @@
 #include <stdarg.h>
 #include <stddef.h>
 
+// define this globally (e.g. gcc -DPRINTF_INCLUDE_CONFIG_H ...) to include the
+// printf_config.h header file
+// default: undefined
+#ifdef PRINTF_INCLUDE_CONFIG_H
+#include "printf_config.h"
+#endif
+
 
 #ifdef __cplusplus
 extern "C" {