In Build Settings page, Invoking add->build more than once skips name prompt

Steps to reproduce:
1. Create a new project
2. In build settings page, add a new build configuration. It prompts for configuration name.
3. Try to add a new build configuration again. It skips the name prompt.

Here is the relevant code:
https://qt.gitorious.org/qt-creator/qt-creator/source/378d6682873281d9f318907687da66905a6efc72:src/plugins/projectexplorer/buildsettingspropertiespage.cpp#L237

The attached patch fixes the problem by restoring the original displayName of the BuildInfo object after use. From what I gathered, the BuildInfo is property of the build configuration factory, and it should not be mutated in this context, but I can't say for sure.