Add more entries to .gitignore files

This is a consecutive patch to my previous patch, it extends the .gitignore
files to work more thoroughly on Windows.

browser/.gitignore:
    ignore .net .dll assemblies

compiler/.gitignore:
    ignore *.obj

extras/.gitignore:
    Ignore the tags directory
    Ignore: *.bat, *.lib,
    Ignore *.dll rather than lib*.dll because the .net assemblies are not
    prefixed.

extras/dynamic_linking/.gitignore:
    Ignore *.out (test output files)

extras/error/.gitignore:
    Ignoring unix binary for the error utility

extras/lex/tests/.gitignore:
    Ignore the test_regex binary

extras/moose/tests/.gitignore:
    Ignore array_based.m because it is generated from array_based.moo
Change extras/net/*.m file mode to 0644

extras/net/net.m:
extras/net/sockets.m:
extras/net/tcp.m:
    chmod 644