MFC r284743:
Rename __weak to __weak_symbol to avoid language conflict with objective-C.

PR: 200972 (exp-run)
Suggested by: theraven@

MFC r268137, r268138:

Define a "__weak" macro for declaring symbols "weak".

Add support for empty data sets. Data set begin and end pointers
should resolve to "NULL" when not present. This is done by declaring
the data set begin and end symbols as "weak".

MFC r284743:
Rename __weak to __weak_symbol to avoid language conflict with objective-C.

PR: 200972 (exp-run)
Suggested by: theraven@

MFC r268137, r268138:

Define a "__weak" macro for declaring symbols "weak".

Add support for empty data sets. Data set begin and end pointers
should resolve to "NULL" when not present. This is done by declaring
the data set begin and end symbols as "weak".