Eliminate the mysterious games that the Cygwin build plays with the linker
flag variables. DLLLIBS is gone, use SHLIB_LINK like everyone else.
Detect cygipc in configure, after the linker flags are set up, otherwise
configure might not work at all.
Make sure everything is covered by make clean.
Fix the build of the new conversion procedure modules.
Add new DLLIMPORT markers where required.
Finally, the compiler complains if we use an explicit
-I/usr/local/include, so don't do that. Curiously, -L/usr/local/lib is
still necessary.
Makefile.port, since they are of no use to configure and much of the
library magic happens in Makefile.port anyway.
Use __alpha, not __alpha__, since the former is universally available.
Remove -DNOFIXADE from the compile command line and put it in the port
include file.
