Revert "page-writeback.c: subtract min_free_kbytes from dirtyable memory"

This reverts commit 338fde9baa6404645b72d76850e55a41faa16636.
Revert "Revert "Low memory killer JBX Mod""

This reverts commit 26fdf965f581c01ff50d9c8a419899790c98a3f9.
Revert "Revert "Add assembler versions of AES and SHA1 for ARM platforms.  This has provided""

This reverts commit e7f408457a0d1e5d3f872cfd0555838cf7bf2cf9.