Improve speed of yaml emitter

[kostja]

It takes over 1 second on my box to output a large Lua table (100k records) to the administrative console. The bottleneck is most likely in the new yaml emitter. In particular, the emitter allocates memory for every node with malloc, so it performs 100k malloc calls.

How it could possibly be improved:

• replace malloc with palloc
• look at other bottlenecks and see what can be improved in yaml token analysis

[ilnarb]

• just use modern allocator, like tcmalloc