Move devlib packages into "general"

The removal of the wheel caching code
(Ia140dc34638d893b92f66d1ba20efd9522c5923b) removed the install of the
"devlib" packages, which was being done with a call in
tools/build_wheels.sh

The idea of "devlibs" and "general" seems to be pretty much the same
thing -- global build requirements.  I have removed the unused devlibs
files, and moved any missing packages into the "general" package
install file.

Change-Id: I8f34a164d6785a122394b42387d4221a7b447ae1
diff --git a/files/debs/general b/files/debs/general
index 80e81f5..7bc90a6 100644
--- a/files/debs/general
+++ b/files/debs/general
@@ -27,3 +27,5 @@
 gettext  # used for compiling message catalogs
 openjdk-7-jre-headless  # NOPRIME
 pkg-config
+libmysqlclient-dev  # MySQL-python
+libpq-dev  # psycopg2