[ScopBuilder] Make -polly-stmt-granularity=scalar-indep the default.

[ScopBuilder] Make -polly-stmt-granularity=scalar-indep the default.

Splitting basic blocks into multiple statements if there are now
additional scalar dependencies gives more freedom to the scheduler, but
more statements also means higher compile-time complexity. Switch to
finer statement granularity, the additional compile time should be
limited by the number of operations quota.

The regression tests are written for the -polly-stmt-granularity=bb
setting, therefore we add that flag to those tests that break with the
new default. Some of the tests only fail because the statements are
named differently due to a basic block resulting in multiple statements,
but which are removed during simplification of statements without
side-effects. Previous commits tried to reduce this effect, but it is
not completely avoidable.

Differential Revision: https://reviews.llvm.org/D42151

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@324169 91177308-0d34-0410-b5e6-96231b3b80d8