[PPCGCodeGeneration] Construct `isl_multi_pw_aff` of PPCGArray.bounds even...

[PPCGCodeGeneration] Construct `isl_multi_pw_aff` of PPCGArray.bounds even when polly-ignore-parameter-bounds is turned on.

When we have `-polly-ignore-parameter-bounds`, `Scop::Context` does not contain
all the paramters present in the program.

The construction of the `isl_multi_pw_aff` requires all the indivisual `pw_aff`
to have the same parameter dimensions. To achieve this, we used to realign
every `pw_aff` with `Scop::Context`. However, in conjunction with
`-polly-ignore-parameter-bounds`, this is now incorrect, since `Scop::Context`
does not contain all parameters.

We set this up correctly by creating a space that has all the parameters
used by all the `isl_pw_aff`. Then, we realign all `isl_pw_aff` to this space.

llvm-svn: 309934