Added some more files to .gitignore. Added technical guidelines for pull requests to CONTRIBUTING

.gitignore

@@ -13,7 +13,20 @@
 *.ilk
 *.lastbuildstate
 vc100.pdb
+ipch
+*.sdf
+*.opensdf
 *.idb
+*.vcxproj
+*.sln
+
+# OSX/Linux build products
+*.mak
+*.mak.vpc_crc
+*.xcodeproj/
+obj*/
+!devtools/*.mak
+!utils/smdlexp/smdlexp.mak
 
 # Specific Source build products
 client.pdb
@@ -23,6 +36,19 @@ server.pdb
 server.dll
 server.lib
 
+client.so
+client.so.dbg
+server.so
+server.so.dbg
+server_srv.so
+server_srv.so.dbg
+
+client.dylib
+client.dylib.dSYM/
+server.dylib
+server.dylib.dSYM/
+
 # files generated by running a mod
 config.cfg
 
+