Have a utility to generate NOTICE from tmux

tmux basically defers to the c files, so
generate a NOTICE file from c files.

genesis/extracttmuxlicenses.py

@@ -0,0 +1,59 @@
+import glob
+yearsbyname = {}
+namesbylicense = {}
+filesbylicense = {}
+for source in glob.glob('*.c'):
+    with open(source, 'r') as sourcein:
+        cap = False
+        thelicense = ''
+        currnames = set([])
+        for line in sourcein.readlines():
+            if '$OpenBSD$' in line:
+                continue
+            if '/*' in line:
+                cap = True
+            elif '*/' in line:
+                cap = False
+                break
+            elif cap:
+                line = line[3:]
+                if line.startswith('Author: '):
+                    continue
+                if line.startswith('Copyright'):
+                    _, _, years, name = line.split(maxsplit=3)
+                    name = name.split('>', 1)[0] + '>'
+                    currnames.add(name)
+                    if name not in yearsbyname:
+                        yearsbyname[name] = set([])
+                    yearsbyname[name].add(years)
+                    continue
+                thelicense += line
+        if thelicense not in namesbylicense:
+            namesbylicense[thelicense] = set([])
+        namesbylicense[thelicense].update(currnames)
+        if thelicense not in filesbylicense:
+            filesbylicense[thelicense] = set([])
+        filesbylicense[thelicense].add(source)
+#        with open(source + '.license', 'w') as liceout:
+#            liceout.write(thelicense)
+
+for license in namesbylicense:
+    for file in sorted(filesbylicense[license]):
+        print('File: ' + file)
+    print('')
+    for author in namesbylicense[license]:
+        years = []
+        for year in sorted(yearsbyname[author]):
+            if not years:
+                years.append(year)
+                continue
+            if int(years[-1].split('-')[-1]) == int(year) - 1:
+                if '-' in years[-1]:
+                    years[-1] = years[-1].split('-', 1)[0] + '-' + year
+                else:
+                    years[-1] = years[-1] + '-' + year
+            else:
+                years.append(year)
+        authline = 'Copyright (c) {} {}'.format(','.join(years), author)
+        print(authline)
+    print("\n" + license + "\n\n")