This branch attempts to improve the detection of covering indexes. This

This branch attempts to improve the detection of covering indexes.  This
first check-in merely improves a parameter name to sqlite3WhereBegin() to
be more descriptive of what it contains, and ensures that a subroutine is
not inlines so that sqlite3WhereBegin() runs slightly faster.

FossilOrigin-Name: cadf5f6bb1ce0492ef858ada476288e8057afd3609caa18b09c818d3845d7244