Vstr is a string library designed for network communication. Its
design uses blocks of ptr+length data, so adding, substituting, and
deleting data are all fast operations. It has a full API of all the
usual string tasks: searching, comparing, splitting, substitution,
converting between upper and lower case, and parsing numbers and
strings. Has a full POSIX and ISO 9899:1999 compliant printf()
implementation including gcc warning compatible custom formatters.
