Add the "stmts" virtual table to the amalgamation, activated when compiled

Add the "stmts" virtual table to the amalgamation, activated when compiled
using -DSQLITE_ENABLE_STMTSVTAB.  Add the SQLITE_STMTSTATUS_REPREPARE and
SQLITE_STMTSTATUS_RUN statistics outputs from sqlite3_stmt_status() and add
corresponding columns to the stmts virtual table.  Change the numeric value
of SQLITE_STMTSTATUS_MEMUSED to get it out of the way of counter values.

FossilOrigin-Name: 88976ae31c2cbc8b75f162140d1356132f69e5b30786e39ad8ca5a1774b03621