Change definitions of bitmap flags to bit-shifting style

The attached patch changes definitions like

#define FOO 0x01
#define BAR 0x02

to

#define FOO (1 << 0)
#define BAR (1 << 1)

etc.

Both styles are currently in use, but the latter style seems more
readable and easier to update.

This change only addresses bitmaps used in memory (e.g., for parsing or
specific function APIs), where the actual bits don't really matter.
Bits that might go on disk weren't touched. There, defining the bits in
a more concrete way seems better.