Expose syntax errors for mini-languages

[andychu]

• echo -e -- invalid backslash escape
• glob, in GlobToERE -- there are some backslash issues, invalid character class, etc.
  • parser returns self.warnings which are not exposed!
• PS1 -- invalid backslash escape
• brace_range: we have errors, but we blame the whole thing rather than individual tokens
  • TODO: since this must appear on a single line, we can do the math to print the
    correct syntax error?

Other:

• Invalid utf-8 for ${s:1:3} -- needs location info
  • and ${#s}, although I'm considering changing that to bytes!

[andychu]

Added strict-glob and strict-backslash spellings for this (not implemented)

[andychu]

prerequisite: SimpleLexer has to deal with token instances with locations, instead of (Id, val) pairs

[andychu]

• Use new Token representation for SimpleLexer to add location info #837 is the related refactoring