Simulation plot zoom-in displays incorrect Y-range (lp:#1674132)

[Original report](https://bugs.launchpad.net/bugs/1674132) created by **Imre Deak (ideak)**
```
Application: kicad
Version: (2017-03-18 revision 98e3bfb)-master, release build
Libraries: wxWidgets 3.0.2
           libcurl/7.50.1 GnuTLS/3.5.3 zlib/1.2.8 libidn/1.33 librtmp/2.3
Platform: Linux 4.10.0-rc8+ x86_64, 64 bit, Little endian, wxGTK
- Build Info -
wxWidgets: 3.0.2 (wchar_t,wx containers,compatible with 2.8)
Boost: 1.61.0
Curl: 7.50.1
KiCad - Compiler: GCC 6.2.0 with C++ ABI 1010
        Settings: USE_WX_GRAPHICS_CONTEXT=OFF
                  USE_WX_OVERLAY=OFF
                  KICAD_SCRIPTING=ON
                  KICAD_SCRIPTING_MODULES=OFF
                  KICAD_SCRIPTING_WXPYTHON=ON
                  KICAD_SCRIPTING_ACTION_MENU=OFF
                  BUILD_GITHUB_PLUGIN=ON
                  KICAD_USE_OCE=OFF

Simulating the following circuit:
http://electronics.stackexchange.com/questions/292901/capacitor-polarity-
in-lamp-flasher

producing the following Spice .listing:

Circuit: KiCad schematic
KiCad schematic
1 : kicad schematic
2 : .global gnd
5114 : .model pn2222a npn (is=14.34f xti=3 eg=1.11 vaf=74.03 bf=255.9
ne=1.307 ise=14.34f ikf=.2847 xtb=1.5 br=6.092 nc=2 isc=0 ikr=0 rc=1
cjc=7.306p mjc=.3416 vjc=.75 fc=.5 cje=22.01p mje=.377 vje=.75 tr=46.91n
tf=411.1p itf=.6 vtf=1.7 xtf=3 rb=10)
5138 : .model pn2907 pnp (is=650.6e-18 xti=3 eg=1.11 vaf=115.7 bf=231.7
ne=1.829 ise=54.81f ikf=1.079 xtb=1.5 br=3.563 nc=2 isc=0 ikr=0 rc=.715
cjc=14.76p mjc=.5383 vjc=.75 fc=.5 cje=19.82p mje=.3357 vje=.75 tr=111.3n
tf=603.7p itf=.65 vtf=5 xtf=1.7 rb=10)
5428 : vv1 net-_q2-pad3_ 0 dc 8
5429 : rr1 net-_q2-pad3_ npnb 63k
5430 : rr2 npnb 0 5.6k
5431 : rr4 vout 0 200
5432 : cc1 vout npnb 22u
5433 : qq1 pnpb npnb 0 pn2222a
5434 : qq2 vout pnpb net-_q2-pad3_ pn2907
5435 : .save@ vv1[i]
5436 : .save@ rr1[i]
5437 : .save@ rr2[i]
5438 : .save@ rr4[i]
5439 : .save@ cc1[i]
5440 : .save@ qq1[ib]
5441 : .save@ qq1[ic]
5442 : .save@ qq1[ie]
5443 : .save@ qq2[ib]
5444 : .save@ qq2[ic]
5445 : .save@ qq2[ie]
5446 : .save v(0)
5447 : .save v( 0 )
5448 : .save v(net-_q2-pad3_)
5449 : .save v(vout)
5450 : .save v(npnb)
5451 : .save v(pnpb)
5452 : .control
5453 : listing
5454 : .endc
5455 : .tran 100u 1
5457 : .end
Background thread stopped with timeout = 0
Doing analysis at TEMP = 27.000000 and TNOM = 27.000000
Initial Transient Solution
--------------------------
Node                                   Voltage
----                                   -------
net-_q2-pad3_                                8
npnb                                  0.631761
vout                                   7.88666
pnpb                                   7.17048
vv1#branch                           -0.040181
 Reference value :  0.00000e+00
No. of Data Rows : 10148


adding the following signals to the plot:
I(C1)
V(Vout)
V(npnb)
V(pnpb)

and then zooming in with the mouse cursor to the -7V to 15V, 0.4s to 0.45s
Y/X range displays incorrectly the -4V to 18V, 0.4s to 0.45s Y/X range.
```
Original tags: eeschema ngspice

Story points: 10.0