ENH: Separate the notion of a request for LFS and its availability.  Allow user code to block definitions of LFS macros.  Added framework to give error if sys/types.h is included before this header when LFS is requested (currently disabled).

ENH: Exposed pattern->regex API.  Cleaned up and commented implementation of pattern->regex conversion.

BUG: strlen logic was backwards resulting in function body never actually executing... when called with valid strings, it was always doing nothing and returning false... now it works as expected.

COMP: Use SA_RESTART only if it is defined for the current platform.  This partially addresses bug#3556.

BUG: When handing the child stdin pipe a file, allow another process to be writing to the file at the same time.  This allows children such as tail -f to function properly.