Format preprocessor macros more consistently

Within the libjpeg API code, it seems to be more the convention than not
to separate the macro name and value by two or more spaces, which
improves general readability.  Making this consistent across all of
libjpeg-turbo is less about my individual preferences and more about
making it easy to automatically detect variations from our chosen
formatting convention.  I intend to release the script I'm using to
validate this stuff, once it matures and stabilizes a bit.

jchuff.h

@@ -20,9 +20,9 @@
  */
 
 #if BITS_IN_JSAMPLE == 8
-#define MAX_COEF_BITS 10
+#define MAX_COEF_BITS  10
 #else
-#define MAX_COEF_BITS 14
+#define MAX_COEF_BITS  14
 #endif
 
 /* Derived data constructed for each Huffman table */