Revert "lib/flex_proportions.c: fix corruption of denominator in flexible proportions"

This reverts commit ff6fb130133b200b605b8dced8f5f63587927cc3.
Revert "lib: Fix possible deadlock in flexible proportion code"

This reverts commit 5af5f46dedb718d36d3b29d7313dc6f2dee361ca.
Revert "lib: Proportions with flexible period"

This reverts commit 475a81235e64e3304d26600da773f1ee59887c38.
Revert "lib/memcopy: use glibc version"

This reverts commit 241cc8eaf95bbcf48ed7e0c4dad2ae12c0c2a237.