Small AI ASCII grid file files are not recognised as a supported file format

[peifer]

According to aaigriddataset.cpp, line 426, small files with less than 100 bytes do not look like an AI ASCII grid file. This results in into ERROR 4 when trying to read the following legitimate, but only 62 byte large file:

$ cat test.asc
ncols     1
nrows     1
xllcorner 0
yllcorner 0
cellsize  1
0

$ gdalinfo test.
test.asc  test.tif
[peifer@whitefish:tmp]> gdalinfo test.asc
ERROR 4: `test.asc' not recognised as a supported file format.

gdalinfo failed - unable to open 'test.asc'.