Use new syntax highlighting engine from zyedidia/highlight

This changes all the syntax files in the runtime directory and also
changes how syntax highlighting is done from inside micro.

runtime/syntax/tex.yaml

@@ -0,0 +1,31 @@
+filetype: tex
+
+detect: 
+    filename: "\\.tex$|bib|\\.bib$|cls|\\.cls$"
+
+rules:
+    # colorize the identifiers of {<identifier>} and [<identifier>]
+    - identifier:
+        start: "\\{"
+        end: "\\}"
+        rules: []
+    - identifier:
+        start: "\\["
+        end: "\\]"
+        rules: []
+    # numbers
+    - constant.number: "\\b[0-9]+(\\.[0-9]+)?([[:space:]](pt|mm|cm|in|ex|em|bp|pc|dd|cc|nd|nc|sp))?\\b"
+    # let brackets have the default color again
+    - default: "[{}\\[\\]]"
+    - special: "[&\\\\]"
+    # macros
+    - statement: "\\\\@?[a-zA-Z_]+"
+    # comments
+    - comment:
+        start: "%"
+        end: "$"
+        rules: []
+    - comment:
+        start: "\\\\begin\\{comment\\}"
+        end: "\\\\end\\{comment\\}"
+        rules: []