compile: implement library search to support MSVC static linking

compile: implement library search to support MSVC static linking

* lib/compile (func_cl_wrapper): Implement library search and
-static option so that the user can select whether to prefer
dll import libraries or static libraries.  This enables MSVC to
link against dlls generated by libtool without requiring libtool
or workarounds such as -lfoo.dll etc.  Makes the tests/static.at
test case in libtool pass.
* tests/compile3.test: Don't trip up if there happens to exist
a "foo" library in the library search path.
* tests/compile6.test: New test, verifying the library search.
* tests/Makefile.am (TESTS): Update.

Signed-off-by: Peter Rosin <peda@lysator.liu.se>