header (C) fixes
IPRT: -Wunused-parameter.
gcc-4.6 warnings (shadowed declaration)
tstRTAssertCompile.cpp: Postpone array problem on MSC.
iprt/assert.h: Added AssertCompileMembersAtSameOffset, AssertCompileMembersSameSize and AssertCompileMembersSameSizeAndOffset + testcase.