Add support for FontForge time stamp table

Fixes https://github.com/behdad/fonttools/issues/56

Doc/documentation.html

@@ -42,7 +42,7 @@ When using TTX from the command line there are a bunch of extra options, these a
 The following tables are currently supported:
 <BLOCKQUOTE><TT>
 <!-- begin table list -->
-BASE, CBDT, CBLC, CFF, COLR, CPAL, DSIG, EBDT, EBLC, GDEF, GMAP, GPKG, GPOS, GSUB, JSTF, LTSH, META, OS/2, SING, SVG, TSI0, TSI1, TSI2, TSI3, TSI5, TSIB, TSID, TSIJ, TSIP, TSIS, TSIV, VORG, cmap, cvt, fpgm, gasp, glyf, hdmx, head, hhea, hmtx, kern, loca, maxp, name, post, prep, sbix, vhea and vmtx
+BASE, CBDT, CBLC, CFF, COLR, CPAL, DSIG, EBDT, EBLC, FFTM, GDEF, GMAP, GPKG, GPOS, GSUB, JSTF, LTSH, META, OS/2, SING, SVG, TSI0, TSI1, TSI2, TSI3, TSI5, TSIB, TSID, TSIJ, TSIP, TSIS, TSIV, VORG, cmap, cvt, fpgm, gasp, glyf, hdmx, head, hhea, hmtx, kern, loca, maxp, name, post, prep, sbix, vhea and vmtx
 <!-- end table list -->
 </TT></BLOCKQUOTE>
 Other tables are dumped as hexadecimal data.

Lib/fontTools/ttLib/tables/F_F_T_M_.py

@@ -0,0 +1,46 @@
+from fontTools.misc.py23 import *
+from fontTools.misc import sstruct
+from fontTools.misc.textTools import safeEval
+from ._h_e_a_d import mac_epoch_diff
+from . import DefaultTable
+import time
+import calendar
+
+FFTMFormat = """
+		>	# big endian
+		version:        I
+		FFTimeStamp:    Q
+		sourceCreated:  Q
+		sourceModified: Q
+"""
+
+class table_F_F_T_M_(DefaultTable.DefaultTable):
+
+  def decompile(self, data, ttFont):
+    dummy, rest = sstruct.unpack2(FFTMFormat, data, self)
+
+  def compile(self, ttFont):
+    data = sstruct.pack(FFTMFormat, self)
+    return data
+
+  def toXML(self, writer, ttFont):
+    writer.comment("FontForge's timestamp, font source creation and modification dates")
+    writer.newline()
+    formatstring, names, fixes = sstruct.getformat(FFTMFormat)
+    for name in names:
+      value = getattr(self, name)
+      if name in ("FFTimeStamp", "sourceCreated", "sourceModified"):
+        try:
+          value = time.asctime(time.gmtime(max(0, value + mac_epoch_diff)))
+        except ValueError:
+          value = time.asctime(time.gmtime(0))
+      writer.simpletag(name, value=value)
+      writer.newline()
+
+  def fromXML(self, name, attrs, content, ttFont):
+    value = attrs["value"]
+    if name in ("FFTimeStamp", "sourceCreated", "sourceModified"):
+      value = calendar.timegm(time.strptime(value)) - mac_epoch_diff
+    else:
+      value = safeEval(value)
+    setattr(self, name, value)

Lib/fontTools/ttLib/tables/__init__.py

@@ -12,6 +12,7 @@ def _moduleFinderHint():
 	from . import D_S_I_G_
 	from . import E_B_D_T_
 	from . import E_B_L_C_
+	from . import F_F_T_M_
 	from . import G_D_E_F_
 	from . import G_M_A_P_
 	from . import G_P_K_G_