BUG/MEDIUM: http: cook_cnt() forgets to set its output type

BUG/MEDIUM: http: cook_cnt() forgets to set its output type

Since comit b805f71 (MEDIUM: sample: let the cast functions set their
output type), the output type of a fetch function is automatically
considered and passed to the next converter. A bug introduced in
1.5-dev9 with commit f853c46 (MEDIUM: pattern/acl: get rid of
temp_pattern in ACLs) was revealed by this last one : the output type
remained string instead of UINT, causing the cast function to try to
cast the contents and to crash on a NULL deref.

Note: this fix was made after a careful review of all fetch functions.
A few non-trivial ones had their comments amended to clearly indicate
the output type.