Split LTESTS option into two - one internal and one external

[dibyendumajumdar]

Enabling LTESTS is important for debugging and testing but we need to avoid modifying the data structures in Lua when testing external libraries which would not have the same compiler settings. So we need two modes - LTESTS and LTESTS_MAX - the latter being the current mode, and former a mode where data structures are not impacted

[dibyendumajumdar]

A better option is to always enable LTESTS in debug releases, and avoid using ltests.h. Instead include the extra stuff in lua.h itself so that the changes are deployed in installations, and all debug builds enable the same settings

[dibyendumajumdar]

Released