Prevent optimization if the operand has multiple users.
Transform (x & 0xFFFFFFFC) + (x >> 2) -> lea(x >> 2, x >> 2, 4).

This is a common pattern for x % c.
Fixup for 27215754: Remove additional IRG property flags from remove_bads.

When remove_bads replaces a block, it destroys the additional information
attached to the block (e.g. dominance). Commit 27215754 asserted these
properties in error.