for the tests: fixed "invalid escape sequence" warnings in recent python

Fixes #94

Author: jacobwilliams

test/bspline_extrap_test.f90

@@ -57,7 +57,7 @@ program bspline_extrap_test
     call plt%initialize(grid=.true.,xlabel='x (deg)',ylabel='f(x)',&
                         title='Extrapolation Test',legend=.true.)
     call plt%add_plot(x*rad2deg,fcn_1d,&
-                        label='Function $f(x) = \sin(x)$',&
+                        label='Function $f(x) = \\sin(x)$',&
                         linestyle='ko',markersize=5,linewidth=2,istat=istat)
 
     do j=1,2

test/bspline_linear_test.f90

@@ -52,7 +52,7 @@ program bspline_linear_test
     call plt%initialize(grid=.true.,xlabel='x (deg)',ylabel='f(x)',&
                         title='Linear Test',legend=.true.,figsize=[10,5])
     call plt%add_plot(x,fcn_1d,&
-                        label='Function $f(x) = \sin(x)$',&
+                        label='Function $f(x) = \\sin(x)$',&
                         linestyle='ko',markersize=5,linewidth=2,istat=istat)
 
     errmax = 0.0_wp

test/dbint4_test.f90

@@ -56,7 +56,7 @@ program dbint4_test
     call plt%initialize(grid=.true.,xlabel='x (deg)',ylabel='f(x)',&
                         title='B-Spline End Conditions',legend=.true.)
     call plt%add_plot(x*rad2deg,fcn_1d,&
-                        label='Function $f(x) = \sin(x)$',&
+                        label='Function $f(x) = \\sin(x)$',&
                         linestyle='ko',markersize=5,linewidth=2,istat=istat)
 
     if (extrap) then

test/knot_tests.f90

@@ -41,7 +41,7 @@ program knot_tests
     call plt%initialize(grid=.true.,xlabel='x',ylabel='f(x)',&
                         title='Knot Test',legend=.true.)
     call plt%add_plot(x,fcn,&
-                        label='Function $f(x) = \sin(x \cdot \pi/18)$ : $x=[0,20,40,60,80,100]$',&
+                        label='Function $f(x) = \\sin(x \\cdot \\pi/18)$ : $x=[0,20,40,60,80,100]$',&
                         linestyle='ko--',markersize=5,linewidth=2,istat=istat)
 
     !initialize three with different knot sequences: