Check for python in configure

Summary: Some OSs have python named according to a version ID
e.g. `python2.7` without a symlink from plain `python`

Use autotool's AM_PATH_PYTHON to search for a suitable interpreter
and use that to generate the *Tables.cpp files.

Closes #109

Reviewed By: @yfeldblum

Differential Revision: D2147977

folly/Makefile.am

@@ -321,15 +321,15 @@ nobase_follyinclude_HEADERS = \
 	wangle/ssl/TLSTicketKeySeeds.h
 
 FormatTables.cpp: build/generate_format_tables.py
-	build/generate_format_tables.py
+	$(PYTHON) build/generate_format_tables.py
 CLEANFILES += FormatTables.cpp
 
 EscapeTables.cpp: build/generate_escape_tables.py
-	build/generate_escape_tables.py
+	$(PYTHON) build/generate_escape_tables.py
 CLEANFILES += EscapeTables.cpp
 
 GroupVarintTables.cpp: build/generate_varint_tables.py
-	build/generate_varint_tables.py
+	$(PYTHON) build/generate_varint_tables.py
 CLEANFILES += GroupVarintTables.cpp
 
 libfollybase_la_SOURCES = \

folly/configure.ac

@@ -72,6 +72,9 @@ AX_BOOST_REGEX
 AX_BOOST_SYSTEM
 AX_BOOST_FILESYSTEM
 
+# Check for python interpreter
+AM_PATH_PYTHON
+
 # Checks for header files.
 AC_HEADER_STDC
 AC_CHECK_HEADERS([fcntl.h features.h inttypes.h limits.h stdint.h stdlib.h string.h sys/time.h unistd.h mutex.h malloc.h emmintrin.h byteswap.h bits/functexcept.h bits/c++config.h])