Fix gcc warnings in hud/hudtarget.cpp

declaration of ‘gauge_object’ shadows a member of 'this'
declaration of ‘esct’ shadows a global declaration [-Wshadow]
variable ‘srange’ set but not used [-Wunused-but-set-variable]
variable ‘ship_is_ballistic’ set but not used

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@10955 387891d4-d844-0410-90c0-e4c51a9137d3
Fix Coverity 1093822 Uninitialized scalar variable

Set sensible looking defaults for the elems added to the beam_collision
struct since retail

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@10956 387891d4-d844-0410-90c0-e4c51a9137d3