sqlite amalgamation in third_party

[ahgamut]

Added SQLite to third_party subfolder of Cosmopolitan repo.
Steps to replicate:

• Clone my fork of SQLite https://github.com/ahgamut/sqlite/tree/cosmopolitan
• run superconfigure and then make to obtain sqlite3.c and shell.c
• create custom Make recipe sqlite3.mk based on Makefile obtained above
• copy all necessary SQLite headers for compilation
• change all #includes via find-and-replace to use the Cosmopolitan headers (<math.h> to "libc/math.h" etc.)
• comment out lines to avoid warnings (a few Wredundant-decls)
• Warning: Running clang-format on sqlite3.c requires a lot of RAM (crashed my system when I had 8GB RAM available).

sqlite.com compiles and runs under MODE=dbg and MODE=tiny (1024KB executable with MODE=tiny).

[ahgamut]

Ok, now it is in two commits:

First commit adds sqlite3.c and all the related headers created from f83d501 in the SQLite Github mirror.

Second commit adds sqlite3.mk and all the changes made to build with Cosmopolitan.

[ahgamut]

No need to merge this becase #162 got merged in.