Added regtest for #126

regtest/basic/rt-newline/COLVAR.reference

+#! FIELDS time ang1 ang2
+ 0.000000  0.356  0.059
+ 0.050000  0.377  0.114
+ 0.100000  0.381  0.158
+ 0.150000  0.372  0.187
+ 0.200000  0.373  0.188

regtest/basic/rt-newline/Makefile

+include ../../scripts/test.make

regtest/basic/rt-newline/config

+type=driver
+# this is to test a different name
+arg="--plumed plumed.dat --trajectory-stride 10 --timestep 0.005 --ixyz trajectory.xyz --dump-forces forces --dump-forces-fmt=%10.6f"
+extra_files="../../trajectories/trajectory.xyz"

regtest/basic/rt-newline/plumed.dat

+ang1: ANGLE ATOMS=2,6,3
+ang2: ANGLE ATOMS=2,6,7,3
+
+RESTRAINT ...
+  ARG=ang2
+  KAPPA=20.0
+  AT=0.8
+...
+
+PRINT STRIDE=10 ARG=ang1,ang2 FILE=COLVAR FMT=%6.3f
\ No newline at end of file