#2739 CDB file symbol record not generated for absolute addressed variables

[Aaron Perl]

Using the "__at" keyword to assign an absolute address to a variable causes SDCC to not generate a symbol record in the adb or cdb files for that variable when the debug flag is specified. A linker record is still correctly generated for the variable when the cdb file is generated from the adb files. We suspect this has to do with the variable having an absolute address but not being an SFR based on a brief look at the SDCC source code that constructs the symbol table. We have only tested this on MCS51.