Fix path issue in windows.

hat-tip to @JamesEarlDouglas for original fix with this info:

Under Windows, when Eclipse imports a project it will replace
'C:\foo\bar\baz' with 'foo/bar/baz', dropping the 'C:\' and
replacing backslashes with forward slashes.  This causes
a problem in Eclipse, because it can't resolve 'foo/bar/baz'
as being on the C drive.  This fix adds an explicit replaceAll
from backslashes to forward slashes, which prevents Eclipse
from doing it wrongly.

sbteclipse-core/src/main/scala/com/typesafe/sbteclipse/core/Eclipse.scala

@@ -229,7 +229,7 @@ private object Eclipse extends EclipseSDTConfig {
               <link>
                 <name>{ name }</name>
                 <type>2</type>
-                <location>{ location.getCanonicalPath }</location>
+                <location>{ location.getCanonicalPath.replaceAll("\\\\", "/") }</location>
               </link>
           }
         }