Parse clang warnings with "In file included from"

[ethercrow]

Example:

clang: warning: -lpthread: 'linker' input unused
In file included from /home/user/project/src/Thingy.cpp:7:
/home/user/project/src/Thingy.hpp:9:1: error: unknown type name 'name'
name space stuff {
^
/home/user/project/src/Thingy.hpp:9:11: error: expected ';' after top level
      declarator
name space stuff {
          ^
          ;
2 errors generated.