Uses <glibtop/mountlist.h> to get list of mountpoints.
Compile with:
clang src/mounttable.c  -std=c99  $(pkg-config --libs --cflags blkid glib-2.0 libgtop-2.0) -Wall -Wextra -D_RM_COMPILE_MAIN -D_BSD_SOURCE -Wall -Wextra -D_RM_HASH_LEN=16  -DHAVE_MOUNTLIST=1 -DHAVE_BLKID=1

Hashtable structure is not quite right yet.  Need to be able to map file dev_t (which is different to block device dev_t) to physical device name (sda etc).
Changed mapping of hashtable from st_rdev to st_dev
(btrfs subvolumes report 0 for st_rdev)
Fixed small memory leak in mounttable.c