[PhilipDeegan]

Fixes:

• iwyu was given the compile command minus only its first word, so with ccache g++ ... it got g++ as an input file (error: no such file or directory: 'g++'). The flags are now taken with Compilers::identify, like clang.tidy.
• The iwyu profile configured the module under init (it only implements compile) and had no src, so CI never ran iwyu.
• The format profile used style: google, which ignores .clang-format (SortIncludes: false) and moved mkn/mod/init.hpp last, breaking the build. Now style: file.
• headers args are only passed for header files, previously .cpp files were also checked as headers.
• types accepts space or : separated values as the README says, ignore accepts a list.
• mkn.yaml drops the ${MKN_HOME} maiken dependency, only mkn.mod headers are used.
• CI runs apt-get update before installing iwyu.

New options:

• fix: <args>: iwyu output is written to <build dir>/iwyu.out and passed to fix_include with these args. Only the checked files are edited (iwyu also reports on headers of other projects), --basedir is set so the paths match. fix: "" for fix_include defaults.
• system_last: true: with fix, system includes are moved after project includes in the files fix_include edited.

Tested on Linux: module self-check, scratch projects, and mkn.avx (19 files edited, tests still build except test_all, where grid.hpp uses is_aligned from vector.hpp inside a template without including it). Windows cmd /c path for fix is untested.