v2:
* Include tzmap.h in BUILT_SOURCES
* Make per-file flags appear after user-supplied CXXFLAGS, so they can
override optimization level.
* Correct .o files used to define symbols exported by libm.a
* Drop gcrt0.o mistakenly included in libgmon.a
* Add missing line continuations in GMON_FILES value
v3:
* use per-file flags for .c compilation
* override C{XX,}FLAGS, as they are set on the command line by top-level make
v4:
* Drop -Wno-error=write-strings from path_testsuite CXXFLAGS
v5:
* Update for changes in master
- Add -fno-threadsafe-statics to CXX flags
- Add hypotl.cc
- Remove fenv.cc (in favour of newlib), add fenv.c stub
- Add proc.5 manpage rules
