Added SelectGlyphsSplines and SelectGlyphsReferences scripting functions
Added ChangeWeight scripting function.
Allow bItalic() to take a second argument for the xheight percentage.
If script filename doesn't exist, look instead for one ending in .ff
or .pe
Don't bother looking for serifs in a sans-serif font.
Revert "Don't bother looking for serifs in a sans-serif font."

This reverts commit 8fc90f40324b1b992ba5439ba8095e1cac9b6077.
Disabled buggy code in bApplySubstitution()
Unknown function/script file errors should be reported in the caller's
context.