Fix automatic delimiters detection

[danon]

Currently, pattern()/Pattern::of()/new Pattern(), each "guess" whether a pattern is delimited (with flags) or not.

This is ambiguous, for example:

• is /abc/m delimited? Of course
• is _abc_m delimited? pattern() would say yes
• is ,(word),x delimited? pattern() would see ,(word), and x flag.
• is ,(word),xF delimited? suddenly, xF are not valid flags so pattern() would see ,(word),xF with no flags.
• is //s an empty pattern with s flag? Or //s pattern? pattern() would choose the first

So:

• we must remove automatic delimiter detection, because it causes too much ambiguity
• pattern()/Pattern::of() will now treat each pattern as undelimited by default. Validation will be performed, whether we have enough delimiters to delimit it properly. If we don't, the other method will have to be used.
• New method will have to be added Pattern::pcre(), which will only accept a delimited pattern, that is:
  • Having a delimiters at the start and end of a string (+ additional flags).
  • No validation of pattern used with the new method should be done, in hope that PCRE by itself will validate it.

New method name, perhaps:

• Pattern::standard() - standard pattern for PCRE, not so much for T-Regx
• Pattern::basic()
• Pattern::pcre() - unintuitive
• Pattern::undelimited() - too long
• Pattern::raw() - too crude

[danon]

But now problem arises:

• You can't now pass an arbitrary string and validate it pattern('/hello?/')->is()->valid() :/
• Possible solutions:
  • two methods? Like Pattern::of()/Pattern:pcre(), but for pattern()?
  • Improve pattern guessing:
    • Only allow for guessing of certain, unambiguous delimiters (/, #)
    • Parse flags
    • Restore is() method

[danon]

Basically, to throw an arbitrary string, go

Pattern::pcre('/hello?/m')->valid();

To validate T-Regx style patterns, go:

pattern('hello?', 'm')->valid();
Pattern::of('hello?', 'm')->valid();