refactor($compile): simplify regular expressions

Closes #9637

Author: Taritsyn

src/ng/compile.js

@@ -680,8 +680,8 @@ $CompileProvider.$inject = ['$provide', '$$sanitizeUriProvider'];
 function $CompileProvider($provide, $$sanitizeUriProvider) {
   var hasDirectives = {},
       Suffix = 'Directive',
-      COMMENT_DIRECTIVE_REGEXP = /^\s*directive\:\s*([\d\w_\-]+)\s+(.*)$/,
-      CLASS_DIRECTIVE_REGEXP = /(([\d\w_\-]+)(?:\:([^;]+))?;?)/,
+      COMMENT_DIRECTIVE_REGEXP = /^\s*directive\:\s*([\w\-]+)\s+(.*)$/,
+      CLASS_DIRECTIVE_REGEXP = /(([\w\-]+)(?:\:([^;]+))?;?)/,
       ALL_OR_NOTHING_ATTRS = makeMap('ngSrc,ngSrcset,src,srcset'),
       REQUIRE_PREFIX_REGEXP = /^(?:(\^\^?)?(\?)?(\^\^?)?)?/;
 
@@ -2434,7 +2434,7 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
   }];
 }
 
-var PREFIX_REGEXP = /^(x[\:\-_]|data[\:\-_])/i;
+var PREFIX_REGEXP = /^((?:x|data)[\:\-_])/i;
 /**
  * Converts all accepted directives format into proper directive name.
  * All of these will become 'myDirective':