add more keyboard sequences as per rfc1548
copy of https://bitbucket.org/rsc/plan9port/commits/aab26b664432/

Reference: /n/atom/patch/applied/kbdadd
Date: Tue Jan  7 05:21:11 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /lib/keyboard	Tue Jan  7 05:20:54 2014
+++ /lib/keyboard	Tue Jan  7 05:20:56 2014
@@ -385,6 +385,8 @@
 00044E  @yu         ю	cyrillic small letter iu
 00044F  @ya         я	cyrillic small letter ia
 000451  @yo         ё	cyrillic small letter io
+001E3E  'M          Ḿ latin capital letter m with acute
+001E3F  'm          ḿ latin small letter m with acute
 002018  l'          ‘	single turned comma quotation mark
 002019  r'          ’	single comma quotation mark
 00201C  l"          “	double turned comma quotation mark
@@ -484,10 +486,12 @@
 002211  su          ∑	n-ary summation
 002213  -+          ∓	minus-or-plus sign
 002217  **          ∗	asterisk operator
+002218  co          ∘	composition operator
 00221A  sr          √	square root
 00221D  pt          ∝	proportional to
 00221E  if          ∞	infinity
 002220  an          ∠	angle
+002225  pp          ∥	parallel to
 002227  l&          ∧	logical and
 002228  l|          ∨	logical or
 002229  ca          ∩	intersection
@@ -532,16 +536,23 @@
 00229C  =O O=       ⊜	circled equals
 0022A2  tu          ⊢	right tack
 0022A8  Tu          ⊨	true
+0022B2  ld          ⊲ normal subgroup of
+0022B3  rd          ⊳ contains as normal subgroup
 0022C0  L&          ⋀	n-ary logical and
 0022C1  L|          ⋁	n-ary logical or
 0022C2  CA          ⋂	n-ary intersection
 0022C3  CU          ⋃	n-ary union
 0022C4  lz          ⋄	diamond operator
+0022C8  bt          ⋈ bowtie operator
 0022DC  =<          ⋜	equal to or less than
 0022DD  =>          ⋝	equal to or greater than
 0022E6  <!~         ⋦	less than but not equivalent to
 0022E7  >!~         ⋧	greater than but not equivalent to
 0022EF  el          ⋯	midline horizontal ellipsis
+00230A  lf          ⌊ left floor
+00230B  rf          ⌋ right floor
+002329  </          〈 left angle bracket
+00232a  />          〉 right angle bracket
 002423              ␣	open box, visible space
 002639  :(          ☹ sad face
 00263A  :)          ☺ smiley face
@@ -562,6 +573,8 @@
 00266d  Mb          ♭	music flat
 00266e  M#          ♮	music natural
 00266f  Ms          ♯	music sharp
+00300a  <+          《	left double angle bracket
+00300b  +>          》	right double angle bracket
 00F015  ZA          	raw alt (plan 9 specific)
 00F016  ZS          	raw shift (plan 9 specific)
 00F017  ZC          	raw ctl (plan 9 specific)