[MachO] Tweak handling of LC_FUNCTION_STARTS

[bdash]

LC_FUNCTION_STARTS includes both functions and jump tables. We want to avoid calling AddFunctionForAnalysis on jump tables since it can result in a function being created at the jump table's location with a bogus body.

We already skip adding functions for entries in LC_FUNCTION_STARTS if the lifting of their first few bytes end up including LLIL_UNDEF. However, arm64 intentionally lifts udf instructions (i.e., opcodes in the Permanently Undefined range) to LLIL_TRAP in order to preserve the immediate portion of the instruction.

To address this, MachoView::IsValidFunctionStart now returns false if the first lifted instruction is LLIL_TRAP in addition to when the lifting contains LLIL_UNDEF.

[bdash]

This prevents functions like this from being created:

00045b7c    void jump_table_45b7c() __noreturn

00045b7c     0  0c000000   udf     #0xc
{ Does not return }

Instead they are displayed as jump table data like so:

00045b7c  uint32_t jump_table_45b7c[0x58] = 
00045b7c  {
00045b7c      [0x00] = __macho_header.filetype
00045b80      [0x01] = __macho_section_64_[6][4]
00045b84      [0x02] = data_3dc
00045b88      [0x03] = 0x25c
00045b8c      [0x04] = 0x21c
00045b90      [0x05] = 0x27c
00045b94      [0x06] = 0x31c
00045b98      [0x07] = 0x3fc
00045b9c      [0x08] = 0x43c
00045ba0      [0x09] = 0x468