Added US EN keymap for Ubuntu 12.04.

Per https://github.com/kernc/logkeys/issues/88, the existing
-u option didn't map correctly on Ubuntu 12.04.

keymaps/en_US_ubuntu_1204.map

+<Esc>
+1 ! 1
+2 @
+3 #
+4 $
+5 %
+6 ^
+7 &
+8 *
+9 ( 9
+0 ) 0
+- _
+= + =
+<BckSp>
+<Tab>
+q Q
+w W
+e E
+r R
+t T
+y Y
+u U
+i I
+o O
+p P
+[ {
+] }
+<Enter>
+<LCtrl>
+a A
+s S
+d D
+f F
+g G
+h H
+j J
+k K
+l L
+; : ;
+' " '
+` ~ `
+<LShft>
+\ |
+z Z
+x X
+c C
+v V
+b B
+n N
+m M
+, < ,
+. > .
+/ ? /
+<RShft>
+<CpsLk>
+<LAlt>
+ 
+<CpsLk>
+<F1>
+<F2>
+<F3>
+<F4>
+<F5>
+<F6>
+<F7>
+<F8>
+<F9>
+<F10>
+<NumLk>
+<ScrLk>
+<KP7>
+<KP8>
+<KP9>
+<KP->
+<KP4>
+<KP5>
+<KP6>
+<KP+>
+<KP1>
+<KP2>
+<KP3>
+<KP0>
+<KP.>
+Ĉ
+<F11>
+<F12>
+<KPEnt>
+<RCtrl>
+<KP/>
+<PrtSc>
+<AltGr>
+<Break>
+<Home>
+<Up>
+<PgUp>
+<Left>
+<Right>
+<End>
+<Down>
+<PgDn>
+<Ins>
+<Del>
+<Pause>
+<LMeta>
+<RMeta>
+<Menu>