delete autotools .gitignore files

One special case, `src/util/xmlpool/.gitignore` is not entirely deleted,
as `xmlpool.pot` still gets generated (eg. by `ninja xmlpool-pot`).

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

src/util/.gitignore

@@ -1,3 +0,0 @@
-format_srgb.c
-u_atomic_test
-roundeven_test

src/util/tests/hash_table/.gitignore

@@ -1,12 +0,0 @@
-collision
-delete_and_lookup
-delete_management
-destroy_callback
-insert_and_lookup
-insert_many
-null_destroy
-random_entry
-remove_key
-remove_null
-replacement
-clear

src/util/xmlpool/.gitignore

@@ -1,8 +1 @@
-ca
-de
-es
-fr
-nl
-sv
-options.h
 xmlpool.pot