[RFC: PATCH] lockdep: Make MAX_STACK_TRACE_ENTRIES configurable.

[John Kacur]

This patch was created against v2.6.33.2-rt13 but is also intended for 
mainline.

Certain debug configurations tend to go over the MAX_STACK_TRACE_ENTRIES
limit without there really being any problem.

This patch keeps the old default, but allows the user to configure a 
higher value if desired.

I tend to bump this value up for real-time debug configurations for 
example. This is preferrable to indiscriminately turning off the locking 
correctness validator.

There have been some attempts to increase the default value in the past, 
that were met with resistance by some, because of the legitimate concern 
that this was growing too large and that we need to understand why. By 
making it configurable, I hope to satisfy both sets of people - those who 
believe they need to set it larger under special circumstances, and those 
who want a reasonably small default.