made SnippetGraphNodeCount count the right thing; re-enable prepared snippet graph caching by default
remove use of snippets for lowering nop write barriers
replaced global snippet and template node metrics with per-snippet and per-template metrics
mx_graal.py symlink for commands.py for static import
Test case for loop unrolling.
Invalidate cached nodes after canonicalization in full unrolling.
Canonicalize coversions that don't change the type.
SL: Enhanced SimpleLanguage with support for if statements, function calls, function caching + inlining and builtins.

--HG--
rename : graal/com.oracle.truffle.sl/src/com/oracle/truffle/sl/NodeFactory.java => graal/com.oracle.truffle.sl/src/com/oracle/truffle/sl/SLNodeFactory.java
rename : graal/com.oracle.truffle.sl/src/com/oracle/truffle/sl/nodes/FunctionDefinitionNode.java => graal/com.oracle.truffle.sl/src/com/oracle/truffle/sl/nodes/FunctionRootNode.java
rename : graal/com.oracle.truffle.sl/src/com/oracle/truffle/sl/SLArguments.java => graal/com.oracle.truffle.sl/src/com/oracle/truffle/sl/runtime/SLArguments.java
Merge.
SL: fixed eclipse formatter problems.