Build lexer and parser from libCom/Makefile.
Since libCom now includes asLib.c and asLib_lex.c we must build
antelope and flex without linking them to Com. This works because
they only need epicsTempFile anyway. However make doesn't like a
subdirectory with the same name as a target object, so the antelope
source directory is now called yacc. The two main.c files were also
renamed to avoid other build problems.
Merge asHost into Com and remove mentions in CONFIG_BASE
Lots of noise since SRCS must be renamed to Com_SRCS
Each SRC_DIR gets its own Makefile fragment, and where it needs
private build rules a RULES files.
If this pattern gets used elsewhere we could automate the include
lines (search $(SRC_DIRS) for Makefiles and RULES files?).
