build: remove --shared-cares configure switch

c-ares is a) bundled with libuv now, and b) contains out-of-tree patches. It no
longer makes sense to link against a shared library.

Fixes #2117.

configure

@@ -83,21 +83,6 @@ parser.add_option("--no-ssl2",
     dest="no_ssl2",
     help="Disable OpenSSL v2")
 
-parser.add_option("--shared-cares",
-    action="store_true",
-    dest="shared_cares",
-    help="Link to a shared C-Ares DLL instead of static linking")
-
-parser.add_option("--shared-cares-includes",
-    action="store",
-    dest="shared_cares_includes",
-    help="Directory containing C-Ares header files")
-
-parser.add_option("--shared-cares-libpath",
-    action="store",
-    dest="shared_cares_libpath",
-    help="A directory to search for the shared C-Ares DLL")
-
 parser.add_option("--shared-zlib",
     action="store_true",
     dest="shared_zlib",
@@ -257,16 +242,6 @@ def configure_v8(o):
     o['variables']['node_shared_v8_includes'] = options.shared_v8_includes
 
 
-def configure_cares(o):
-  o['variables']['node_shared_cares'] = b(options.shared_cares)
-
-  # assume shared_cares if one of these is set?
-  if options.shared_cares_libpath:
-    o['libraries'] += ['-L%s' % options.shared_cares_libpath]
-  if options.shared_cares_includes:
-    o['include_dirs'] += [options.shared_cares_includes]
-
-
 def configure_openssl(o):
   o['variables']['node_use_openssl'] = b(not options.without_ssl)
 
@@ -307,7 +282,6 @@ output = {
 configure_node(output)
 configure_libz(output)
 configure_v8(output)
-configure_cares(output)
 configure_openssl(output)
 
 # variables should be a root level element,