Config option for ES6 exp operator

config/config-options/DUK_USE_ES7_EXP_OPERATOR.yaml

@@ -0,0 +1,10 @@
+define: DUK_USE_ES7_EXP_OPERATOR
+introduced: 2.0.0
+default: true
+tags:
+  - ecmascript
+  - ecmascript7
+description: >
+  Support the ES7 exponentation operator (** and **=).  This is optional
+  because the operator pulls in pow() which may have a significant footprint
+  impact on bare metal platforms.

config/examples/low_memory.yaml

@@ -89,3 +89,4 @@ DUK_USE_REGEXP_CANON_WORKAROUND: false
 DUK_USE_COROUTINE_SUPPORT: false
 DUK_USE_SOURCE_NONBMP: false  # <300 bytes footprint
 DUK_USE_ES6_PROXY: false  # roughly 2kB footprint
+DUK_USE_ES7_EXP_OPERATOR: false  # pulls in pow()

config/tags.yaml

@@ -9,6 +9,9 @@ ecmascript:
 ecmascript6:
   title: Ecmascript Edition 6 (ES6) feature options
 
+ecmascript7:
+  title: Ecmascript Edition 7 (ES7) feature options
+
 compliance:
   title: Compliance related options