coalesce_after_aligning_divs: use isl_bool instead of int as variable
This variable was introduced in
a73f222ef9 (isl_map_coalesce: only
coalesce pairs of basic maps with the same divs, Tue Apr 17 19:05:00
2012 +0200) and forgotten to convert in
370a8b7d (introduce isl_bool and
isl_stat return types, Mon May 4 09:45:16 2015 +0200). This commit
changes the type of 'known' from int to isl_bool. To avoid implicit
conversions by returning a variable of type isl_bool in a function returning
isl_change, we return explicit isl_change values. This change improves
readability and helps static analysis tools.
Signed-off-by: Sven Verdoolaege <sven.verdoolaege@gmail.com>