Delete unused litstr conversion functions

These aren't called, so this takes them off the table.
Remove dumpDebugInfo (dead code)

it's dead
Clean up TranslatorX64

This is a bunch of cleanup I've done for my work on the
region translator that isn't strictly releated to the region
translator.

- Move irTranslate* methods up to Translator and rename them
  translate*.
- Remove a bunch of friend declarations from TranslatorX64.
- Remove emitVariantGuards. We don't translate pseudomains so it was
  never doing anything anyway.
- Remove the unused REQ_BIND_REQUIRE.
Kill m_localsOffset and free another 16 bytes of memory

Users of m_localsOffset used this offset to calculate pointer where
local variables starts. Since they are stored in the reverse order, the
equation was:

  cont_ptr + m_localsOffset + num_locals - local_id - 1

We are already storing pointer to ActRec (m_arPtr), which is equal to:

  cont_ptr + m_localsOffset + num_locals

This diffs kills m_localsOffset and uses m_arPtr to simplify
calculations. Continuation fields were rearranged so that
sizeof(c_Continuation) is reduced by 16 bytes.
Provide a config option to turn off debugger prompt.

The debugger prompt string depends on user/machine specific configuration settings, which makes its inclusion in expected test output problematic. There is already an option in (the user controlled) ~/.hphpd.hdf to turn off the prompt. Now there is an option in normal config files to do the same.
make PHP_SAPI dynamic based on execution mode

It isn't really a constant anyways.

Closes #757