`cwr3_lmg_m60e3` lack magazine compatibility

[Drofseh]

The CWR3 M60E3 cwr3_lmg_m60e3 can only use the four 100rnd M240 belts from CUP and is not compatible with 7.62 belts from other mods suchs as NIA/HLC and FWA.

See the CUP M60 CUP_lmg_M60 for comparison.

The CBA CBA_762x51_LINKS magwell should be added to cwr3_lmg_m60e3 to add compatiblity.