Add PCB milling and () comments testcase.

While neither PCB milling nor comments in parentheses are
part of the innermost core or RepRap printing, they happen
and should be handled gracefully.

testfiles/PCB-milling-and-(comment).gcode

+(Created by G-code exporter)
+(Fri Apr 27 22:20:09 2012)
+(Board size: 100.00 x 130.00 mm)
+(---------------------------------)
+G21
+G90
+G0 X14.392 Y30.94113 Z1.
+G4
+M104 S255
+G1 Z-0.2 F60
+G1 X14.05334 Y30.60247
+G1 X12.02134 Y30.60247
+G1 X11.598 Y30.85647
+G1 X11.00534 Y31.5338
+G1 X10.074 Y32.5498
+G1 X9.98933 Y34.41247
+G0 Z1.
+(RepRap Gen7 v1.4)
+G0 Z1.
+(R)
+G0 X9.9753 Y6.9723
+G1 Z-0.20 F60
+G1 X11.4761 Y6.9723 F250
+G1 X11.8514 Y6.5971
+G1 X11.8514 Y5.8467
+G1 X11.4761 Y5.4715
+G1 X10.3505 Y5.4715
+G1 X11.8514 Y3.9456
+G0 Z1.
+G0 X10.3505 Y6.9723
+G1 Z-0.20 F60
+G1 X10.3505 Y3.9456 F250
+G0 Z1.
+(e)
+G0 X12.7519 Y4.696
+G1 Z-0.20 F60
+G1 X14.2778 Y4.696 F250
+G1 X14.2778 Y5.0962
+G1 X13.9025 Y5.4715
+G1 X13.1271 Y5.4715
+G1 X12.7519 Y5.0962
+G1 X12.7519 Y4.3208
+G1 X13.1271 Y3.9456
+G1 X14.2778 Y3.9456
+G0 Z1.
+(p)
+G0 X15.5535 Y2.8199
+G1 Z-0.20 F60
+G1 X15.5535 Y5.0962 F250
+G1 X15.1783 Y5.4715
+G1 X15.5535 Y5.0962
+G1 X15.9287 Y5.4715
+G1 X16.6792 Y5.4715
+G1 X17.0544 Y5.0962
+G1 X17.0544 Y4.3208
+G1 X16.6792 Y3.9456
+G1 X15.9287 Y3.9456
+G1 X15.5535 Y4.3208
+G0 Z1.
+G4
+M104 S0
+(tool change position)
+G1 X2. Y2. Z40. F400
+M2