Put the standard mmc flags in one file.

STANDARD_MCFLAGS:
    Put the mmc options that are common to either

    - all of the dir/DIR_FLAGS.in files, or
    - all but one of them,

    into this new file.

    (MFILTERJAVAC_FLAGS did not specify --warn-suspicious-foreign-code;
    after this diff, it does.)

configure.ac:
    Enable replacing @STANDARD_MCFLAGS@ with the new file's contents.

browser/MDB_FLAGS.in:
compiler/COMP_FLAGS.in:
deep_profiler/DEEP_FLAGS.in:
grade_lib/GRADE_LIB_FLAGS.in:
library/LIB_FLAGS.in:
mdbcomp/MDBCOMP_FLAGS.in:
mfilterjavac/MFILTERJAVAC_FLAGS.in:
profiler/PROF_FLAGS.in:
slice/SLICE_FLAGS.in:
ssdb/SSDB_FLAGS.in:
    Include STANDARD_MCFLAGS instead of listing each option in it
    individually, making future global changes to options easier.

mfilterjavac/MFILTERJAVAC_FLAGS.in

@@ -1,20 +1,6 @@
 @BOOTSTRAP_MC_ARGS@
---no-infer-all
---warn-known-bad-format-calls
---warn-unknown-format-calls
---warn-non-contiguous-clauses
---warn-non-contiguous-foreign-procs
---warn-inconsistent-pred-order-clauses
---warn-unused-imports
---warn-insts-with-functors-without-type
---warn-potentially-ambiguous-pragma
---halt-at-warn
---no-halt-at-warn-make-int
---no-halt-at-warn-make-opt
+@STANDARD_MCFLAGS@
 --no-warn-inferred-erroneous
---no-allow-ho-insts-as-modes
---no-mercury-stdlib-dir
---no-detect-libgrades
 -I../ssdb
 -I../browser
 -I../library