fix heap.c overflowing
add double support to mysql_helper
lhashtable: added put_key
add list_clear
vmbuf_remove_last_if, minor improvement
ringfile: fixed initializer
add LIST_NULL_INITIALIZER
make mysql optional also for examples
http_server: configurable bind addr
add/fix sprintf check
thashtable (temp hashtable) using ribs_malloc
resize ringfile
thashtable: add foreach
thashtable: use struct instead of void in type
thashtable use calloc when growing
add vmbuf_replace_last_if

replaces the last character from a vmbuf with a different one if
it matches.

useful when iterating through a list to remove the trailing ','
that will be generated otherwise.

additionally refactor remove_last_if as a special case.
use vmbuf_replace_last_if