Add support for vmp_prepare_dblptr

[Pro7ech]

Comments

Originally the signature for vmp_prepare_dblptr had the comments

/** @brief prepares a vmp matrix (mat[row*ncols+col] points to the item) */

I'm not sure if this indexing was intentional or not, as it would mean the matrix has row*col rows and each column is of size N. After using spqlios for things such as circuit bootstrapping, it is much more convenient to have the indexing done as mat[row]+col*N, or equivalently, each row is a vec_znx and each column a limb of the vec_znx indexed by the row. This allow to prepare a matrix (e.g. RGSW) from a set of vec_znx (a e.g. set of RLWE) by simply constructing an array pointing to each of their data.

Changes

• Added vmp_prepare_row which enables to prepare the i-th row of a vmp_pmat for vec_znx, vec_rnx, vec_zn32. This enables to prepare a vmp_pmat with a buffer as small as one row (a vec_znx).
• Added support for vmp_prepare_dblptr for vec_znx, vec_rnx, vec_zn32. vmp_prepare_dblptr sequentially calls vmp_prepare_row.
• Added tests for vmp_prepare_dblptr for vec_znx, vec_rnx, vec_zn32 (which also directly tests vmp_prepare_row).
• Renamed vmp_prepare_contiguous_tmp_bytes to vmp_preapre_tmp_bytes.
• Removed some duplicates in module API.

Related Issues

#46, #47