This patch adds some missing error handling to PGTYPESnumeric_div() in
ecpg's pgtypeslib: (1) we need to check the return value of sub_abs()
(2) we need to check the return value of 4 calls to digitbuf_alloc().
Per Coverity static analysis by EDB.
Barring any objections I'll apply this to CVS later today.
-Neil