array#comparison
Added a test for Math.erf
The added test now passes.
Added test for erfc
test for erfc passes
Added test for lgamma

Apparently the first part of the test already worked so the interesting one is
the second one: Math.lgamma(-1) should return [infinity, 1].
Implemented lgamma(-1)

Along the way I noticed some errors in my test for this feature. So the correct
test is also a part of this commit.
Added a test for lgamma(NaN)
Fixed buggy test

The test I added previously is incorrect because in Python the equation
"float('NaN') == float('NaN')"
returns False.
I use math.isnan now to check whether a float represents NaN.
Fixed the lgamma(NaN) issue

rubyspec/core/math/lgamma_spec.rb can be untaged with --untranslated now.
Using rfloat.erf[c] instead of math.erf[c]

rfloat is imported from rpython.rlib
Therefor I hope that it won't let the translation crash.
Merge remote-tracking branch 'origin/master' into comparison
refactor try_convert
Using RPython inf and NaN instead of Python ones
Found a better way to let the lgamma-specs pass

The first components of lgamma(-1) and lgamma(NaN) are actually calculated
correctly by rfloat.lgamma. It's the second components that cause the spec to
fail. So in the current version only the calculation of the second component is
modified.
Proc#=== is alias for Proc#call

Fixes specs:

Proc#===
- invokes self
- sets self's parameters to the given values
- can receive block arguments

Proc#=== on a Proc created with Proc.new
- replaces missing arguments with nil
- silently ignores extra arguments
- auto-explodes a single Array argument

Proc#=== on a Proc created with Kernel#lambda or Kernel#proc
- ignores excess arguments when self is a proc
- substitutes nil for missing arguments when self is a proc
- treats a single Array argument as a single argument when self is a lambda
- treats a single Array argument as a single argument when self is a proc
Proc#yield is an alias for Proc#call

Fixes specs:

Proc#yield
- invokes self
- sets self's parameters to the given values
- can receive block arguments

Proc#yield on a Proc created with Proc.new
- replaces missing arguments with nil
- silently ignores extra arguments
- auto-explodes a single Array argument

Proc#yield on a Proc created with Kernel#lambda or Kernel#proc
- ignores excess arguments when self is a proc
- substitutes nil for missing arguments when self is a proc
- treats a single Array argument as a single argument when self is a lambda
- treats a single Array argument as a single argument when self is a proc
Tagged failing spec for Proc#===
Merge pull request #613 from krekoten/proc_call

Alias `Proc#yield` and `Proc#===` to `Proc#call`
Merge pull request #566 from kostya/comparison

array#comparison