Fix final target name calculation
antimake: use JoinPath when calculating feat file name
antimake: show mkdir commands if in verbose mode
antimake: convert mkdir and printf to functions.

Then it's possible to examine and change arguments.
antimake: make OBJEXT include '.'

Now the usage is same as EXEEXT.
antimake: support LIBDIR

Now different extension can be used for static libraries.
antimake: don't clean LDADD/LIBADD files
antimake: call hooks also for EXTRA targets
antimake: clean also EXTRA targets
antimake: make sure DEPENDENCIES and nodist_SOURCES exist before build starts.

Old way tied them to final link, which is too late.
antimake: mkdir is not needed in ar_lib
antimake: dont use readpath when loading extensions

Seems it's not reliable.
antimake: use printf instead of echo
antimake: keep per-object mkdir always quiet
antimake: safer test result print
antimake: follow symlinks when searching extensions
antigen: --help switch, test for configure.ac
amext-msvc.mk: MSVC toolchain support from libusual

requires:
- plain cmd.exe
- make from gnuwin32
- coreutils from gnuwin32

it does not work with mingw32/msys yet.