loadtxt: increase length of internal buffers (#893)

Author: perazz

Diff for: src/stdlib_io.fypp

@@ -120,7 +120,7 @@ contains
       !!
       integer :: s
       integer :: nrow, ncol, i, ios, skiprows_, max_rows_
-      character(len=128) :: iomsg, msgout
+      character(len=1024) :: iomsg, msgout
 
       skiprows_ = max(optval(skiprows, 0), 0)
       max_rows_ = optval(max_rows, -1)
@@ -214,7 +214,7 @@ contains
       !!
 
       integer :: s, i, ios
-      character(len=128) :: iomsg, msgout
+      character(len=1024) :: iomsg, msgout
       s = open(filename, "w")
       do i = 1, size(d, 1)
         #:if 'real' in t1