[MERGE #1089] linux: slightly improve code for max VAS values
[MERGE #1089] linux: slightly improve code for max VAS values

Merge pull request #1089 from xanlpz:linux
Document a bit better the values for 64 and 32bit builds and
consolidate the used values in one place. Best we can do for #1059 I think.

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