Simplify compilation with nvfortran and xlf (#496)

Author: vyu16

src/json_parameters.F90

@@ -57,14 +57,14 @@ module json_parameters
     character(kind=CK,len=*),parameter :: dot             = CK_'.'  !! path separator for [[json_get_by_path_default]]
     character(kind=CK,len=*),parameter :: tilde           = CK_'~'  !! RFC 6901 escape character
     character(kind=CK,len=*),parameter :: single_quote    = CK_"'"  !! for JSONPath bracket-notation
-    character(kind=CK,len=*),parameter :: slash           = CK_'/'  !! JSON special character
-    character(kind=CK,len=*),parameter :: backslash       = CK_'\'  !! JSON special character
     character(kind=CK,len=*),parameter :: quotation_mark  = CK_'"'  !! JSON special character
     character(kind=CK,len=*),parameter :: bspace          = achar(8,  kind=CK) !! JSON special character
     character(kind=CK,len=*),parameter :: horizontal_tab  = achar(9,  kind=CK) !! JSON special character
     character(kind=CK,len=*),parameter :: newline         = achar(10, kind=CK) !! JSON special character
     character(kind=CK,len=*),parameter :: formfeed        = achar(12, kind=CK) !! JSON special character
     character(kind=CK,len=*),parameter :: carriage_return = achar(13, kind=CK) !! JSON special character
+    character(kind=CK,len=*),parameter :: slash           = achar(47, kind=CK) !! JSON special character
+    character(kind=CK,len=*),parameter :: backslash       = achar(92, kind=CK) !! JSON special character
 
     !> default real number format statement (for writing real values to strings and files).
     !  Note that this can be overridden by calling [[json_initialize]].