WFS OCG filter rgex tests for numeric values

[assefa]

regex test for numeric values in filter encoding (mapogcfilter.c:FLTIsNumeric function) was using: [-+]?
b([0-9]*
.[0-9]+|[0-9]+)
b

It should use:

^{[-+]?[0-9]*
.?[0-9]+$}

[assefa]

committed in r9777

using this to account for scientific notations: "^{[-+]?[0-9]*
.?[0-9]+([eE][-+]?[0-9]+)?$"}

[assefa]

backported in the 5.6.x branch r9910