This reverts commit f6ba7b06.

Hide a bunch of debug logging statements in #ifdef SHOW_DEBUG to prevent spinning a mutex in hot paths.

Use _mm_setzero and _mm_set1 instead of static global variables for the SIMD epsilon and zero vectors as this generates better code under modern compilers

LLWearableType::initSingleton() calls LLWearableDictionary::initParamSingleton().
LLWearableDictionary's constructor constructs specific WearableEntry
instances, each of which wants to translate its name string to a user-facing
label using LLWearableType::mTrans.

WearableEntry's constructor was calling LLWearableType::getInstance(). Under
circumstances we don't fully understand (recursive mutex misbehavior?), that
could hang.

Instead, pass the canonical LLWearableType instance to LLWearableDictionary's
constructor, and from there into WearableEntry's constructor.

Replace dynamic_cast with static_cast as these never actually need or seem to be checked, except the one.

Provide method of storing joint indices sep from weight data for faster runtime processing.

Revert attempted fix for 10625.

Fix OSX compiler error from missing defaulted param and changed signature of renderAlphaMaskTextures.

Add work-around for broken intel drivers which can't use glReadPixels from RGBA FBOs to get alpha without locking up.