Add support for 'ldflags_extra' in build system.

This patch adds the ability to specify extra (additional) flags to the
linker when bsl_gyp.py is executed (by adding a command line option
similar to '-D ldflags_extra=<flags>'). This parallels the existing
'cflags_extra' support.
Eliminate reliance on special CLANG_GNUC_* macros.

The BSL platform header relied on custom preprocessor macros that had
to be provided by the build system when Clang was used to compile. These
have been replaced with hardcoded values that configure the code to act
as if Clang was GCC 4.4.0.
Disable inlining for 'Debug' builds on GCC-type compilers.

Inlining interferes with debugging and also interferes with code
coverage analysis, so this patch disables it for Debug builds
when GCC or a compatible compiler is being used.
Replace cout calls with printf calls.   I am leaving iostream in the includes for now, so this compiles.   The macros are handled in a separate branch and that will take care of all macro couts
remove cout in comments
Correctly sort the group 2 includes.
alphabetize the group 2 includes
Alphabetize group 2 includes
Separate bslalg includes into group 1 includes.

In group 1 includes, the first include is for this component and then alphabetize the rest of group 1.
alphabetize lines in group 2 includes.
alphabetize the group 2 includes
alphabetize group 2 includes
alphabetize group 2 includes

make 3 groups of includes
put 3rd party includes (and native std includes) in group 3 includes which don't need to be alpbetized
make 3 groups of includes
in group 1 we must include the component's .h file first
then alpha sort the rest of group 1

in group 2 the includes are now alphabetized

moved iterator into the group 3 includes.. group 3 doesn't need to be alphabetized.
make 3 groups of includes
In group 1, the component's .h is first stringbuf.h
In group 1, all the other includes are alphabetized

In group 2, all the other includes are alphabetized

I brought together the 3rd party includes together in group 3 includes
Merge branch 'alphabetize_includes' of https://github.com/weiyeh/bsl into alphabetize_includes