Bug 354446 remove "core" from .gitignore

The 'core' and 'core.*' entries are causing the filtering out of
valid files given our typical package naming convention
containing the word "core". We must remove these entries so that
new files in these folders are flagged as being untracked.
diff --git a/.gitignore b/.gitignore
index 144b5bf..e474e81 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,11 +2,9 @@
 *~
 *.rej
 *.bak
-core
 *.patch
 javacore.*
 heapdump.*
-core.*
 Snap.*
 target/