Updated to most recent version RE2 and remove upstreamed patches.

third_party/re2/doc/syntax.txt

 RE2 regular expression syntax reference
 -------------------------­-------­-----
 
 Single characters:
-.       any character, including newline (s=true)
+.       any character, possibly including newline (s=true)
 [xyz]   character class
 [^xyz]  negated character class
 \d      Perl character class
 \D      negated Perl character class
 [:alpha:]       ASCII character class
 [:^alpha:]      negated ASCII character class
 \pN     Unicode character class (one-letter name)
 \p{Greek}       Unicode character class
 \PN     negated Unicode character class (one-letter name)
 \P{Greek}       negated Unicode character class
@@ skipping 37 matching lines @@
 (?flags)        set flags within current group; non-capturing
 (?flags:re)     set flags during re; non-capturing
 (?#text)        comment NOT SUPPORTED
 (?|x|y|z)       branch numbering reset NOT SUPPORTED
 (?>re)  possessive match of «re» NOT SUPPORTED
 re@>    possessive match of «re» NOT SUPPORTED vim
 %(re)   non-capturing group NOT SUPPORTED vim
 
 Flags:
 i       case-insensitive (default false)
-m       multi-line mode: ^ and $ match begin/end line in addition to begin/end text (default false)
+m       multi-line mode: «^» and «$» match begin/end line in addition to begin/end text (default false)
 s       let «.» match «\n» (default false)
 U       ungreedy: swap meaning of «x*» and «x*?», «x+» and «x+?», etc (default false)
 Flag syntax is «xyz» (set) or «-xyz» (clear) or «xy-z» (set «xy», clear «z»).
 
 Empty strings:
 ^       at beginning of text or line («m»=true)
 $       at end of text (like «\z» not «\Z») or line («m»=true)
 \A      at beginning of text
 \b      at word boundary («\w» on one side and «\W», «\A», or «\z» on the other)
 \B      not a word boundary
@@ skipping 290 matching lines @@
 (*SKIP) NOT SUPPORTED
 (*THEN) NOT SUPPORTED
 (*ANY)  set newline convention NOT SUPPORTED
 (*ANYCRLF)      NOT SUPPORTED
 (*CR)   NOT SUPPORTED
 (*CRLF) NOT SUPPORTED
 (*LF)   NOT SUPPORTED
 (*BSR_ANYCRLF)  set \R convention NOT SUPPORTED pcre
 (*BSR_UNICODE)  NOT SUPPORTED pcre