DtSvc: vastly simplify building this library

DtSvc: vastly simplify building this library

We take advantage of subdir-object and just build the subdir source
files directly as normal dependencies of libDtSvc in the top level
Makefile.am.

This means the intevening subdirectory Makefiles are no longer needed,
and no need to replicate flags and the like between the
subdirectory Makefile.am files.

Also, no need to build fake .a libs we can't really use.

configure: remove AC_OUTPUT_FILES related the the lib/DtSvc/*
subdirectories.  They are no longer needed.