Always use AC_LANG_WERROR when checking for compiler warning flags

Many gcc-compatible compilers (icc, clang, etc.) verbosely ignore
gcc command line flags issuing a warning of some sort.  Catch these
warnings and turn them into errors when checking for support of
specific warning flags.
const'ify string literals and char pointers that needn't be changed

librdfa (start_element): const'ify umap_key

librdfa (rdfa_complete_object_literal_triples): const'ifty current_object_literal

rapper (print_graph): const'ify label
Cosmetics, make make V=0 look good

Using automake's AM_V_GEN trickery to hide the lex and bison calls.
This will also hide compiler warnings erupting from generated code.
Merge pull request #14 from hroptatyr/compiler-support

Intel C compiler (icc) support
Add some GCC5 warning flags
Trailing ,
Add BSD header checks from sort_r
Use __FUNCTION__ (c99) replacing __func__ (c90)
Further fix flex/bison rules to silence them in normal runs
#changes
Support full URLs for typeof.

librdfa commit 5b73975a778ee00f328457356a69163911d540a5
Update 0295 output
Tidy failure output
0197 now fails, 0302 now passes.
0197 passes
0134 passes
fix 134 out
Fix error report again
0235 passes
26 failures