Import awk-20110810.

Import awk-20110810.

* /pat/, \n /pat/ {...} is now legal, though bad style to use.
* added checks to new -v code that permits -vnospace
* removed fixed limit on number of open files
* fixed day 1 bug that resurrected deleted elements of ARGV when
  used as filenames (in lib.c).
* minor type fiddles to make gcc -Wall -pedantic happier (but not
  totally so)
* split(s, a, //) now behaves the same as split(s, a, "")
* another fix to avoid core dump with delete(ARGV)