[1.4>master] [MERGE #2310 @dilijev] Fix VSO 10259529: Add assertion to satisfy analysis of descriptors[descCount]
[1.4>master] [MERGE #2310 @dilijev] Fix VSO 10259529: Add assertion to satisfy analysis of descriptors[descCount]

Merge pull request #2310 from dilijev:bug10259529

Fix VSO 10259529: Add assertion to satisfy analysis of descriptors[descCount] in JavascriptObject::DefinePropertiesHelperForGenericObjects.

Fix some OACR warnings about non-const locals in JavascriptObject.cpp since I was already fixing an OACR warning in the area.

mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore