Issue #1421330 by Albert Volkman, heyrocker: Crosslink cache_set() and cache_get() documentation with @see.

#644482 by hass (backport of #452936): use TRUNCATE to do full cache clearing, which results in a dramatic speed increase

#409994 by Wesley Tanaka, jhodgdon: better documentation on how the cid and wildcard arguments interact on cache_clear_all()

#468732 by andypost: cache_clear_all() mentioned cache_flush_delay incorrectly; it should say we use cache_lifetime

#227228 by ilmaestro, gpk, ball.in.th, catch, andypost: use per-table cache_flush variables to avoid not flushing all but the first table when multiple tables are cleared

#215252 by bdragon: reset the cache flush variable before the cache is flushed, so busy sites will not attempt multiple cache flushes at a time

#195202 by pwolanin: clear block cache before page cache, so stale data will not end up in the cache

noted by Robert Douglass in his caching presentation: the key param to cache_get should be renamed to cid for consistency (all other functions have cid)

#136837 by meba: PHP replaces {} enclosed variables in strings with the variable value itself, so cache tables were not prefixable

- Patch #137415 by slantview: simplified the cache API/usages, and made it a tad smarter.  Makes it easier to program for, and easier to replace.  Will need to be documented.