OS400/initscript.sh: fix db2_name() module name generation

Allow repeatable file name length reduction on file names with underscore or
dash characters. This is done in order to better support libcurl's existing
source file names and allow OS/400 package to build out of the box again.

packages/OS400/initscript.sh

@@ -157,6 +157,10 @@ db2_name()
         basename "${1}"                                                 |
         tr 'a-z-' 'A-Z_'                                                |
         sed -e 's/\..*//'                                               \
+            -e 's/\([^_]\)[^_]*_\(.*\)/\1\2/'                                \
+            -e 's/\([^_]\)\([^_]\)[^_]*_\(.*\)/\1\2\3/'                      \
+            -e 's/\([^_]\)\([^_]\)\([^_]\)[^_]*_\(.*\)/\1\2\3\4/'            \
+            -e 's/\([^_]\)\([^_]\)\([^_]\)\([^_]\)[^_]*_\(.*\)/\1\2\3\4\5/'  \
             -e 's/^\(..........\).*/\1/'
 }