FLEX-34247 improve TLF performance.  I added a flag in case some scenario really needs composition to start from the beginning, but the default is now more like the TLF version that shipped with Adobe Flex 4.6
Merge branch 'develop' of https://git-wip-us.apache.org/repos/asf/flex-tlf into FlexUnit4TestsTLF
Migrate AllCharAttributeTest to Flex Unit 4