Add fast path for construction with no params
Add fast path for construction with no params

This avoids a bunch of code and makes construction of simple objects
faster.

Object construction performance improvement:
         Non-Threaded   Threaded
Simple:           14%         5%
Complex:        -1.1%      -2.2%

Other tests stable.

https://bugzilla.gnome.org/show_bug.cgi?id=557100

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