file-bmp: Fix format specifiers

(cherry picked from commit 1d10c4d88f2138c73446a996685e8febdb138e7f)
file-bmp: Print compression method in debug build

(cherry picked from commit 24cf89aa68b634d76d54995e5f4915466b28b28d)
file-bmp: Use masks when BI_BITFIELDS method is found

(cherry picked from commit 6e73a6278f306c976f068dfd18db9092819aa90d)

Conflicts:
	plug-ins/file-bmp/bmp-read.c