modify iniparser to build unbounded keys & values from multi-line input

Instead of a size limit of ASCIILINESZ for multi-line input now there is no
limit, a multi-line can be *any* size (and hence the key and value now
also have a dynamic size)

* there is a limit still on input line size (since multi lines are built
  from multiple lines where each line part is limited to ASCIILINESZ)
  Note: there is no limit to the size of the multi-line itself (it's
  only limited by available memory)
* all stack & static fixed string usage has been removed with the exception
  of parsing line (or a multi-line portion) input, fgets still reads into
  a fixed string buffer of size ASCIILINESZ.

Signed-off-by: Noel Power <noel.power@suse.com>