grep: fix regression for -F search

[mknos]

• The following search should match, but did not because of the '#' character: perl grep -F '#include' a.c
• This was because quotemeta() was escaping it as \# which was then expanded between single quotes
• The $matcher closure can refer to patterns list directly; this avoids having to expand pattern strings within quotes
• This version is easier to follow because duplicate statements are not added to the closure code if many patterns are specified

  %perl head -n1 a.c
  #include <stdio.h>
  %perl grep -F '#include' a.c
  #include <stdio.h>
  %perl grep -Fi '#includE' a.c
  #include <stdio.h>

[briandfoy]

changes: be more careful with quotemeta and patterns