Update and add .gitignore's

Update and add .gitignore's

This patch adds a bunch of generated files to gdb's gitignore files.
There are still a bunch of "stamp" files that are not ignored, but I
think the rule for them should be put in the top-level gitignore.

Users and developers are encouraged to build out-of-tree, but some
people prefer the simplicity to build in-tree, so it should be useful
for them.

gdb/ChangeLog:

	* .gitignore: Ignore more files.
	* data-directory/.gitignore: Likewise.

gdb/doc/ChangeLog:

	* .gitignore: New file.

gdb/gdbserver/ChangeLog:

	* .gitinore: Ignore more files.

gdb/testsuite/ChangeLog:

	* .gitignore: New file.