Allow option values to contain ':'

Instead, check that option keys don't contain ':'. Also change the
failing option test to look for this.

Closes https://github.com/mesonbuild/meson/issues/1454

mesonbuild/optinterpreter.py

@@ -75,15 +75,16 @@ class OptionInterpreter:
         self.cmd_line_options = {}
         for o in command_line_options:
             if self.subproject != '': # Strip the beginning.
+                # Ignore options that aren't for this subproject
                 if not o.startswith(self.sbprefix):
                     continue
-            else:
-                if ':' in o:
-                    continue
             try:
                 (key, value) = o.split('=', 1)
             except ValueError:
                 raise OptionException('Option {!r} must have a value separated by equals sign.'.format(o))
+            # Ignore subproject options if not fetching subproject options
+            if self.subproject == '' and ':' in key:
+                continue
             self.cmd_line_options[key] = value
 
     def process(self, option_file):

test cases/failing/14 invalid option name/meson_options.txt

@@ -1 +1 @@
-option('invalid/name', type : 'boolean', value : false)
+option('invalid:name', type : 'boolean', value : false)