Refactor Builder into Builder and Builder.Internal modules

--HG--
rename : Data/Text/Lazy/Builder.hs => Data/Text/Lazy/Builder/Internal.hs
Bump version to 0.11.2.4

--HG--
extra : histedit_source : 611167b2d4b27067d25f14b26afe3e6577e26b0d
Add a countDigits function

--HG--
extra : histedit_source : aee87aeba221dc0d9cb40f9fe7bf31f589e8b6d7
Reduce duplication

--HG--
extra : histedit_source : 5c5992ee90e54f83ac0e69a40f43bb228b843348
Float ensureFree way out

--HG--
extra : amend_source : 92cd186bb054e54ad3f8d4a1defe55c2dfdbe98e
extra : histedit_source : 70465aa0273f6e0cee5d628f65660026e4ea6f52
Write straight into the dest buffer

--HG--
extra : amend_source : d9bbf6dc0f7ae7e57c0241434180aad58d07a4f6
extra : histedit_source : 1f35a2b29af13243741d7a3c7abd3637b67e0ce2