qt: Update translations

Update current translations, and add new languages:

- es_MX: Spanish (Mexico)
- pam: Kapampangan

Also update translation process for autoconf-based build system.

doc/translation_process.md

@@ -100,5 +100,7 @@ It is also possible to directly download new translations one by one from the Tr
 
 1. `tx pull -a`
 2. update `src/qt/bitcoin.qrc` manually or via
-   `ls src/qt/locale/*ts|xargs -n1 basename|sed 's/\(bitcoin_\(.*\)\).ts/<file alias="\2">locale/\1.qm<\/file>/'`
-3. `git add` new translations from `src/qt/locale/`
+   `ls src/qt/locale/*ts|xargs -n1 basename|sed 's/\(bitcoin_\(.*\)\).ts/<file alias="\2">locale\/\1.qm<\/file>/'`
+3. update `src/qt/Makefile.am` manually or via
+   `ls src/qt/locale/*ts|xargs -n1 basename|sed 's/\(bitcoin_\(.*\)\).ts/  locale\/\1.ts \\/'`
+4. `git add` new translations from `src/qt/locale/`