document changes for upcoming 0.7.5 release

WHATSNEW

@@ -79,3 +79,22 @@ implemented flockfile, wprintf, and robust mutex functions.
 
 fixed stack corruption bug in times(), minor header bugs, and some
 error return value bugs in thread interfaces.
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+0.7.5 - new features, major optimization, and robustness
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+implemented POSIX timers.
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+optimized and simplified many thread-related functions.
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+eliminated resource leak races in thread cancellation.
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+overhauled stdio implementation to take advantage of readv/writev for
+reduced syscall load, and improved stdio's handling of error status.
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+added syscall header and interface for applications to use and
+greatly simplified internal system for making syscalls.
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+strangthened tmpnam/tempnam/tmpfile filename generation and made the
+straight C functions not depend on POSIX symbols.