pkg2 wip: include julia as a fixed installed "package".
pkg2 wip: provide proxy version numbers for fixed packages.

These proxy versions are necessary for making fixed packages work
properly with version requirements since one has to have a version
for each fixed package against which to evaluate the feasability of
constraints on that package's version to eliminate versions of free
pacakges that won't work with the installed fixed version.
pkg2 wip: on second thought don't let dirtiness affect proxy versions.
add Cwchar_t and update docs. closes #2907
Merge branch 'master' of github.com:JuliaLang/julia
small codegen improvement in is() (use a gc root less often)
pkg2 wip: rename version_number => installed_version.
Values returned by solve methods should match type of rhs

`solve` methods involving a `CholmodFactor` object, whether called
directly or indirectly through methods for `\`, `Ac_div_B`, etc. now
return the same type of object as the right hand side.  If the rhs is
an `Array` they return an `Array`.  Previously these methods returned
a `CholmodDense` or `CholmodSparse` object.
restore commit info to VERSION (and also fix #2912)
test: add tests for version.jl

Follow-up to #2912.