Introduce Charmonizer::Core::CFlags

Move handling of compiler and linker flags to a separate Charmonizer
core class. Charmonizer now uses the following sets of flags:

* cflags: Provided via command line
* extra_cflags: Additional flags
* temp_cflags: Temporary flags used by some probes
Regenerate charmonizer.c
Add chaz_CFlags_add_define
Regenerate charmonizer.c
Use per-parcel defines for symbol visibility

Use macro LUCY_VISIBLE for externally visible symbols. This macro will
be set to CHY_EXPORT when compiling with -DCFP_LUCY and to CHY_IMPORT
otherwise.
Regenerate charmonizer.c
Compile and link test executable with custom flags
Regenerate charmonizer.c
Make lucy_bootstrap_parcel visible
Compile C library with hidden symbols
Regenerate charmonizer.c