Update .gitignore.

Not all git versions understand **/Makefile, but all recognize that
filename without any path applies to all directories.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

.gitignore

@@ -11,7 +11,6 @@
 
 # Top level excludes
 /Makefile.orig
-/Makefile
 /MINFO
 /TABLE
 /*.a
@@ -23,7 +22,8 @@
 /tmp.*
 /configdata.pm
 
-**/Makefile
+# *all* Makefiles
+Makefile
 
 /test/*.ss
 /test/*.srl