[mcs] Handle commas inside quotes correctly

[mcs] Handle commas inside quotes correctly

OpenLiveWriter's build files break due to incorrectly parsing (".",",") as three arguments: a . and two " instead of two: a . and a ,

This is the error:

OpenLiveWriter/writer.build.targets: error : Error executing task WriteLinesToFile: Error converting Property named 'Lines' with value '#define FILE_VERSION $(BuildVersion.Replace(".",","));#define PRODUCT_VERSION $(BuildVersion)' to type Microsoft.Build.Framework.ITaskItem[]: Method 'Replace(., , )' arguments cannot be evaluated'

This patch ignores , as a separator character if it is inside ""