Fix typo: privlidged -> privileged
Another typo: all togethor -> altogether
Make sure the global xhprof config is visible to both the header and footer includes.
Remove unused dir property and constructor param from XHProfRuns_Default. This is a left-over from the Facebook file backend and there should be no compelling reason to retain it anymore.
The MySQL schema doc no longer belongs in XHProfRuns_Default if we are serious about forging ahead with the database abstraction, remove it
Use XHPROF_LIB_ROOT everywhere in index.php
Abstract out the identifier quote style to remove hardcoded MySQL
backticks, also move out FROM_UNIXTIME. Also fixes method declarations
and some variable issues in the database abstractions which leads me to
believe that not all of the database classes actually work. Some minor
refactorings, but at large leaves things be. Inconsistent line endings
and having a mix of spaces and tabs in some places makes the diff a
little less clean than one would wish.

NOTE: The identifier quoting is slavishly done to everywhere to not
change the original code logic, though quoting should be cosmetic for
all but the "server name" field (which really should be renamed while
we're at it).
Add support for PostgreSQL. This required a bunch of more changes to
evict the last hardcoded MySQL details, but the database abstraction
layer seems to be working nicely now for at least MySQL and PostgreSQL
(further testing is encouraged). At least MS SQL and SQL Server seemed
broken from the outset and more work would be required to play ball with
them.

Main changes:

 * added the PostgreSQL db implementation

 * centralized (un)serializing, made things a bit DRYer

 * Use explicit aliases in getRunComparativeData() to not rely on
   implicit MySQL aggregate column naming. Makes the keys prettier too.

 * Added notes about remaining portability issues for other databases
   than MySQL and PostgreSQL.
Remove duplicated logic from getRunComparativeData()