Update of Eclipse project files

- Update of project dependencies
- Deletion of scala-xml project
- Deletion of scala-parser-combinators project
- Update of .gitignore to match nested .cache files
SI-7886 unsoundness in pattern matcher.

I tracked down what was behind the issue described here:

  // TODO: fix the illegal type bound in pos/t602 -- type inference
  // messes up before we get here:
  /*override def equals(x$1: Any): Boolean = ...
         // Span[Any] --> Any is not a legal type argument for Span!
         val o5: Option[com.mosol.sl.Span[Any]] =
  */

...which led straight to the unsoundness seen in neg/t7886.
It is dangerous to have an expected type of "Any" because
the type system will blithely ignore kind errors, since "Any"
can absorb anything. The consequence in this instance was
that inferring the case constructor for a type like

  Foo[T <: Bound]

if done with expected type Any, this would come up with Foo[Any].
I altered it to use expected type Foo[T], which lets the dummy
type parameter survive to carry the bound forward and restores
sense to the inference. The before/after output for -Xprint:patmat
on pos/t602.scala is:

15c15
<         if (x1.isInstanceOf[com.mosol.sl.Span[Any]])
---
>         if (x1.isInstanceOf[com.mosol.sl.Span[K]])
17c17
<             <synthetic> val x2: com.mosol.sl.Span[Any] = \
  (x1.asInstanceOf[com.mosol.sl.Span[Any]]: com.mosol.sl.Span[Any]);
---
>             <synthetic> val x2: com.mosol.sl.Span[K] = \
  (x1.asInstanceOf[com.mosol.sl.Span[K]]: com.mosol.sl.Span[K]);
19,20c19,20
<               val low$0: Option[Any] = x2.low;
<               val high$0: Option[Any] = x2.high;
---
>               val low$0: Option[K] = x2.low;
>               val high$0: Option[K] = x2.high;

A file in the library depended (needlessly) on the unsoundness.
It was easy to fix but reminds us this may affect existing code.
SI-6680 unsoundness in gadt typing.

Introduces -Xstrict-inference to deal with the significant
gap between soundness and what presently compiles. I'm hopeful
that it's TOO strict, because it finds e.g. 75 errors compiling
immutable/IntMap.scala, but it might be that bad.
Rework cff8b569 to heal the windows build.

 - change newTermName to fix negative length names
   rather than reject them
 - restore the old logic in unspecializedName for names that
   result from AnyRef specialized type parameters.

Why does fix the windows build? I remain none the wiser.
Merge pull request #2973 from sschaef/eclipse-update3

Update of Eclipse project files
Merge pull request #3013 from retronym/topic/unspec-fix-windows

Rework cff8b569 to heal the windows build.
Correct build command for scala-ide
Describe type parameter interpolation in @implicitNotFound documentation

Using this feature is necessary for helpful error messages, so it should be documented.

Thank you to @adriaanm for recommending the this description.
Merge pull request #3015 from sschaef/eclipse-update

Correct build command for scala-ide
Merge pull request #3005 from paulp/pr/7886

SI-7886 unsoundness in pattern matcher.
Merge pull request #3014 from ceedubs/pr/implicitNotFound-scaladoc

Describe type parameter interpolation in @implicitNotFound documentation