Revert D120327 "compiler-rt: Add udivmodei5 to builtins and add bitint library"

It has several problems like not-compilable weak attribute with MSVC
(and the usage needs further scrutiny), and " different types for formal and actual parameter"
https://lab.llvm.org/buildbot/#/builders/127/builds/27760/steps/7/logs/stdio

This reverts commit 8843245d, 492c5c05, bf2dc4b3.