Fixes preprocessor syntax highlighting

The line continuation operator is a bit too aggressive so instead of
adding lookaheads for every case where we don't need to apply it
we have excluded the preprocessor directives from the lint cont.

The original .cson highlighting does the same, see:
https://github.com/dparkins/language-fortran/blob/master/grammars/fortran%20-%20free%20form.cson

for injections see:
https://gist.github.com/Aerijo/b8c82d647db783187804e86fa0a604a1

Fixes Preprocessor statements in line continuations break syntax highlighting #248
Fixes Erroneous syntax highlighting for preprocessor conditionals in derived types #249

Author: gnikit

syntaxes/fortran_free-form.tmLanguage.json

@@ -17,10 +17,13 @@
 	],
 	"firstLineMatch": "(?i)-[*]- mode: fortran free -[*]-",
 	"injections": {
-		"source.fortran.free - ( string | comment )": {
+		"source.fortran.free - ( string | comment | source.preprocessor )": {
 			"patterns": [
 				{
 					"include": "#line-continuation-operator"
+				},
+				{
+					"include": "#preprocessor"
 				}
 			]
 		},
@@ -121,6 +124,7 @@
 	],
 	"repository": {
 		"preprocessor": {
+			"name": "source.preprocessor",
 			"begin": "^\\s*(#)",
 			"beginCaptures": {
 				"1": {