EVS files/functions imported

[x] Some of EVS fixed point files/code pulled in as-is.
[x] Changes made in IVAS floating code to maintain floating code and avoid conflicts with newly introduced fixed point code.
[x] Floating code output is bit exact with base version IVAS code.
[x] As EVS changes are taken as-is for initial fixed version creation, the changes are not broken into multiple commits. Hence, the changes involve more number of files.