static params: expr[T] is now static[T]

This introduces tyStatic and successfully bootstraps and handles
few simple test cases.  Static params within macros are no longer
treated as PNimrodNodes - they are now equivalent to constants
of the designated type.
documented static params
make the current PContext accessible through TCandidate

the goal here is to remove all the hacks from ParamTypeMatch and to handle
all type matching in typeRel (the context there is required to evaluate any static
params and to run the compilation tests of user-defined type classes)
wip type class reforms (the compiler bootstraps fine)

* replace tfAny and tfAll with tyAnd and tyOr
* integrate matchTypeClass into typeRel
* introduce tyBuiltInTypeClass to handle types such as tuple, object, proc, etc
better integration of tyStatic into typeRel
test case for semistatic
bugfix: in some contexts, newSeq[T](n) is incorrectly inferred to have a seq[typedesc[T]] type
forgotten modification to the news files
towards support for composite type classes such as seq[Number] and SquareMatrix[T]
lift generic parameters from concrete composite type classes
fix illegal recursion checks
fix tclosure4
fixes #787
make more tests green
integrate the logic of fixupProcType into ReplaceTypeVars
Merge branch 'upstream' into devel

Conflicts:
	compiler/ccgutils.nim
	compiler/msgs.nim
	compiler/sem.nim
	compiler/semexprs.nim
	compiler/seminst.nim
	compiler/semmagic.nim
	compiler/semstmts.nim
	compiler/semtypes.nim
	compiler/semtypinst.nim
	compiler/sigmatch.nim
	compiler/types.nim
	compiler/vmgen.nim
	lib/core/macros.nim
	lib/system.nim
	tests/reject/tenummix.nim
	web/news.txt
fix the filtering of void params in procs' signatures
restore return type inference
proc redefinition search based on the type system instead of on sloppy AST matching

This will work the same for procs/templates/macros/etc, having arbitrary mix of implicit
and explicit generics (as long as the symbols are equivalent for the purposes of overload
resolution, they will be detected as redefinitions)

fixes tgeneric
Introduce a PreMain proc in the C codegen

The rationale here is that it has become too hard to step into a program
when #line directives are enabled. You have to skip over many lines of init
code that doesn't have corresponding lines in the nimrod program.
Now, you can just step-out of PreMain and go straight to the useful code
in NimMain.