The 2.6 version of TypeScript's `resolveModuleName` started to
require paths passed to be separated by '/' instead of being
able to handle '\'.
`ngc` and `ng` already do this transformation.
Fixes: #21811
PR Close#21812
The errors produced when error were encountered while interpreting the
content of a directive was often incomprehencible. With this change
these kind of error messages should be easier to understand and diagnose.
PR Close#20459
Chuck Jazdzewski
Tobias Bosch
Miško Hevery
Jason Aden