Add example for dead code elimination for JSX v4.

DCE does not seem to be working: probably JSC call does not use proper location for the make function.

Author: cristianoc

analysis/reanalyze/examples/deadcode/expected/deadcode.txt

@@ -1101,6 +1101,9 @@
   addRecordLabelDeclaration text ImportMyBanner.res:5:16 path:+ImportMyBanner.message
   addValueReference ImportMyBanner.res:12:4 --> ImportMyBanner.res:7:0
   Scanning JSResource.cmt Source:JSResource.res
+  Scanning JsxV4.cmt Source:JsxV4.res
+  addValueDeclaration +make JsxV4.res:4:23 path:+JsxV4.C
+  addValueReference JsxV4.res:4:36 --> React.res:3:0
   Scanning LetPrivate.cmt Source:LetPrivate.res
   addValueDeclaration +y LetPrivate.res:7:4 path:+LetPrivate
   addValueDeclaration +x LetPrivate.res:3:6 path:+LetPrivate.local_1
@@ -1887,6 +1890,7 @@ File References
   ImportJsValue.res -->> 
   ImportMyBanner.res -->> 
   JSResource.res -->> 
+  JsxV4.res -->> React.res
   LetPrivate.res -->> 
   ModuleAliases.res -->> 
   ModuleAliases2.res -->> 
@@ -2121,6 +2125,7 @@ File References
   Dead Value +ImportMyBanner.+make: 0 references () [0]
   Live Value +ImportMyBanner.+make: 0 references () [0]
   Dead RecordLabel +ImportMyBanner.message.text: 0 references () [0]
+  Dead Value +JsxV4.C.+make: 0 references () [0]
   Live Value +LetPrivate.+y: 0 references () [0]
   Live Value +LetPrivate.local_1.+x: 1 references (LetPrivate.res:7:4) [0]
   Live Value +ModuleAliases.+testInner2: 0 references () [0]
@@ -3981,6 +3986,16 @@ File References
   <-- line 12
   @dead("make") let make = make
 
+  Warning Dead Module
+  File "JsxV4.res", line 3, characters 8-62
+  JsxV4.C is a dead module as all its items are dead.
+
+  Warning Dead Value
+  File "JsxV4.res", line 4, characters 20-47
+  C.make is never used
+  <-- line 4
+    @react.component @dead("C.make") let make = () => React.null
+
   Warning Dead Module
   File "ModuleAliases.res", line 2, characters 10-57
   ModuleAliases.Outer.Inner is a dead module as all its items are dead.
@@ -4505,4 +4520,4 @@ File References
   <-- line 96
   type variant1Object = | @dead("variant1Object.R") R(payload)
 
-  Analysis reported 334 issues (Incorrect Dead Annotation:1, Warning Dead Exception:2, Warning Dead Module:25, Warning Dead Type:89, Warning Dead Value:199, Warning Dead Value With Side Effects:2, Warning Redundant Optional Argument:5, Warning Unused Argument:11)
+  Analysis reported 336 issues (Incorrect Dead Annotation:1, Warning Dead Exception:2, Warning Dead Module:26, Warning Dead Type:89, Warning Dead Value:200, Warning Dead Value With Side Effects:2, Warning Redundant Optional Argument:5, Warning Unused Argument:11)

analysis/reanalyze/examples/deadcode/src/JsxV4.bs.js

@@ -0,0 +1,7 @@
+@@jsxConfig({version: 4})
+
+module C = {
+  @react.component let make = () => React.null
+}
+
+let _ = <C />