sqlite3.go: remove -DSQLITE_DISABLE_INTRINSIC: better builds (#878)

This "disables the use of compiler-specific built-in functions such
as __builtin_bswap32()" (from the SQLite docs) so this change might
produce slightly better code. My primary motivation, however, is that
the "default" configuration for SQLite, which is widely tested, does
not set this preprocessor macro.

From looking at Github issues, it appears this was added to avoid a
build error on Mac OS X 10.11, in 2017:
#386

There have been a number of changes to sqlite3 since we tried this
last. I think it would be worth trying to remove this setting again.
I found a machine running Mac OS X 10.11.6. It was able to build and
run the tests in this package with this change.

Mac OS X 10.11 is has not been supported by Apple since 2018
(currently Apple is releasing updates for Mac OS 10.13 and newer; 11
is the current release). However, Go 1.14 is supported, and it
requires Mac OS X 10.11 or newer: https://golang.org/doc/go1.14
Go 1.15 only supports Mac OS 10.12 and newer:
https://golang.org/doc/go1.15

sqlite3.go

@@ -18,7 +18,6 @@ package sqlite3
 #cgo CFLAGS: -DSQLITE_ENABLE_FTS4_UNICODE61
 #cgo CFLAGS: -DSQLITE_TRACE_SIZE_LIMIT=15
 #cgo CFLAGS: -DSQLITE_OMIT_DEPRECATED
-#cgo CFLAGS: -DSQLITE_DISABLE_INTRINSIC
 #cgo CFLAGS: -DSQLITE_DEFAULT_WAL_SYNCHRONOUS=1
 #cgo CFLAGS: -DSQLITE_ENABLE_UPDATE_DELETE_LIMIT
 #cgo CFLAGS: -Wno-deprecated-declarations