The integer thousands' separator code is rewritten in order to
avoid having to preallocate a buffer for the largest possible
digit string with the most possible instances of the longest
possible multibyte thousands' separator. The new version inserts
thousands' separators for integers using the same code as floating point.
slightly less evil inline functions, and move the buffering state into
a struct. This will make it possible for helper routines to produce
output for printf() directly, making it possible to untangle the code
somewhat.
In wprintf(), use the same buffering mechanism to reduce diffs to
printf(). This has the side-effect of causing wprintf() to catch write
errors that it previously ignored.
