Mark round_up_to_next as inline 
Mark round_up_to_next as inline 

This speeds up rustc on #25916 from 1.36±0.022s to 1.326±0.025s

Tests pass locally (even on 32-bit :-)
aidancully/rust,aidancully/rust,graydon/rust,dwillmer/rust,dwillmer/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,dwillmer/rust,dwillmer/rust,GBGamer/rust,dwillmer/rust,GBGamer/rust,graydon/rust,aidancully/rust,dwillmer/rust,GBGamer/rust,dwillmer/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,dwillmer/rust,GBGamer/rust,GBGamer/rust