Add .hgignore file.

List all generated or temp files in .hgignore, so they
don't clutter the screen when running hg status.
(transplanted from befdb88324e18e1e80260906d0459a56ea0eb37a)

.hgignore

@@ -0,0 +1,25 @@
+syntax: glob
+
+# Generated files
+Makefile
+ct-ng
+docs/ct-ng.1
+docs/ct-ng.1.gz
+paths.mk
+scripts/crosstool-NG.sh
+scripts/saveSample.sh
+scripts/showTuple.sh
+
+# Temporaries
+.*.swp
+log.*
+
+# Working files
+kconfig/conf
+kconfig/mconf
+kconfig/**.o
+kconfig/**.dep
+config.gen/
+.config
+.config.old
+targets/