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
Disabled buggy code in bApplySubstitution()
Unknown function/script file errors should be reported in the caller's
context.
Fix apparent typo in call to utf82u_strncpy.

The original author must have meant ubuf+1 and not ubuf-1, in order to
preserve the space previously inserted at index 0 of ubuf[].