This fixes a "too many sections" issue
```
Fatal error: can't write 159 bytes to section .text of build/libs/ardour/luabindings.cc.1.o: 'file too big'
x86_64-w64-mingw32-as: build/libs/ardour/luabindings.cc.1.o: too many sections (36781)
```
* Windows: delete waf installed .dll.a files
* Windows: override waf's conf.env.LIBDIR = conf.env.BINDIR
with explicit --libdir
* Windows: fix asm (`x86_64-w64-mingw32-as` -D flag is for
debug messages, -D defines are not available)
* Mac: override waf adding -install_name (and
-Wl,-compatibility_version -Wl,-current_version)
by moving -dynamiclib from linkflags to ldflags
* Mac: Allow libs with compat version number suffix
(not needed anymore, but may help in the future)