mke2fs.8.in: add ENVIRONMENT section

Add ENVIRONMENT section and describe behavior of MKE2FS_SYNC,
MKE2FS_CONFIG, MKE2FS_FIRST_META_BG, MKE2FS_DEVICE_SECTSIZE
and MKE2FS_SKIP_CHECK_MSG.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
1 file changed