Fixes to code cache disclaiming

[mpirvu]

Existing code disclaims the cold code between coldCodeAlloc and coldCodeAllocBase. However, if the amount of cold code is larger than the amount of warm code, we will ask to disclaim some parts of the segment which was allocated with THP. This will disable the THP setting and lower throughput. This commit also introduces two new code cache fields that are used to memorize the start and end of the section forced to use small pages and that should be subject to disclaiming.

Signe-off-by: Marius [email protected]