Support constant numbers in inline assembly.

test/libsolidity/syntaxTests/inlineAssembly/constant_access.sol

@@ -0,0 +1,13 @@
+contract C {
+    uint constant x = 2**20;
+    bool constant b = true;
+    bytes4 constant s = "ab";
+    function f() public pure {
+        assembly {
+            let c1 := x
+            let c2 := b
+            let c3 := s
+        }
+    }
+}
+// ----

test/libsolidity/syntaxTests/inlineAssembly/constant_array.sol

@@ -0,0 +1,10 @@
+contract C {
+    string constant x = "abc";
+    function f() public pure {
+        assembly {
+            let a := x
+        }
+    }
+}
+// ----
+// TypeError: (115-116): Only direct number constants are supported by inline assembly.

test/libsolidity/syntaxTests/inlineAssembly/constant_computation.sol

@@ -0,0 +1,9 @@
+contract C {
+    uint constant x = 2**20;
+    function f() public pure {
+        assembly {
+            let a := x
+        }
+    }
+}
+// ----

test/libsolidity/syntaxTests/inlineAssembly/constant_ref.sol

@@ -0,0 +1,11 @@
+contract C {
+    uint constant a = 2;
+    uint constant b = a;
+    function f() public pure {
+        assembly {
+            let x := b
+        }
+    }
+}
+// ----
+// TypeError: (134-135): Only direct number constants are supported by inline assembly.

test/libsolidity/syntaxTests/inlineAssembly/invalid/constant_access.sol

@@ -1,10 +1,9 @@
 contract test {
     uint constant x = 1;
-    function f() public {
+    function f() public pure {
         assembly {
             let y := x
         }
     }
 }
 // ----
-// TypeError: (107-108): Constant variables not supported by inline assembly.

test/libsolidity/syntaxTests/inlineAssembly/invalid/constant_assignment.sol

@@ -7,4 +7,4 @@ contract test {
     }
 }
 // ----
-// TypeError: (98-99): Constant variables not supported by inline assembly.
+// TypeError: (98-99): Constant variables cannot be assigned to.

test/libsolidity/syntaxTests/inlineAssembly/invalid/constant_variable_via_offset.sol

@@ -7,4 +7,4 @@ contract test {
     }
 }
 // ----
-// TypeError: (112-120): Constant variables not supported by inline assembly.
+// TypeError: (112-120): The suffixes _offset and _slot can only be used on non-constant storage variables.